*  JUL  25 1911  *) 

Division  ..  'BFZl 

Section 

\f.\^ 


I 


\ 


Digitized  by  the  Internet  Archive 
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Vol.  XII 
No.  2 


Psychological  Monographs 


November,  1  909 
Whole  No.  49 


THE 


Psychological  Review 


EDITED  BY 
J.  MARK  BALDWIN 


HOWARD  C.  WARREN 
Princeton  University 


JOHN  B.  WATSON 
Johns  Hopkins  University 


AND 


JAMES  R.  ANGELL,  University  of  Chicago  {Editor  of  the  Psychological  Monographs) 


On  the  Influence  of 
Complexity  and  Dissimilarity 

on  Memory 

Harvey  Andrew  Peterson 

Illinois  State  Normal  University,  Normal,  Ill. 


it 


THE  REVIEW  PUBLISHING  COMPANY 

41  NORTH  QUEEN  ST.,  LANCASTER,  PA. 

AND  BALTIMORE,  MD. 


PREFACE. 


While  the  investigation  contained  in  the  following  pages 
belongs  to  the  field  of  pure  psychology,  the  motives  which 
prompted  it  were  considerations  rather  of  educational  psychol¬ 
ogy,  and  it  is  believed  that  not  the  least  of  its  significance  will 
be  found  in  its  bearing  upon  certain  problems  in  this  latter 
field.  The  experiments  were  carried  out  at  the  University  of 
Chicago  during  the  year  1908-9.  The  subjects  were  eleven 
graduate  students  in  the  Department  of  Psychology,  of  whom 
seven  were  men  and  four  women.  Messrs.  E.  B.  McProud, 
W.  C.  Vogt,  H.  Kimmel,  F.  A.  C.  Perrin,  J.  W.  Hayes,  E.  H. 
Sutherland,  and  J.  W.  Baumgardner,  and  Misses  Emma 
Felsenthal,  Mary  C.  McIntosh,  Edith  Turner,  and  Jeanette 
Obenchain.  Two  of  them,  Mr.  McProud  and  Miss  Felsenthal, 
were  obliged  by  pressure  of  other  work  to  withdraw  after  the 
Gray  and  the  Violet  Sets  and  the  Renaissance  Set  had  been 
completed.  Their  places  were  taken  by  Mr.  Baumgardner 
and  Miss  Obenchain.  In  the  latter  part  of  the  year  supple¬ 
mental  experiments,  described  in  V-3,  were  carried  out  with 
Messrs.  Sutherland  and  Hayes  and  Miss  Turner.  They  did 
not  participate  in  the  earlier  experiments. 

For  the  splendid  spirit  in  which  all  eleven  carried  out  their 
part  of  the  investigation  I  wish  to  express  to  them  my  deep 
appreciation  and  heartfelt  thanks.  To  Professor  James  R. 
Angell,  Director  of  the  Laboratory,  and  to  Professor  Harvey 
Carr  and  Dr.  Karl  T.  Waugh  I  am  glad  of  this  opportunity  to 
express  my  sincere  thanks  for  assistance  in  the  formulation 
and  execution  of  the  work. 


Harvey  Andrew  Peterson. 


CONTENTS 


I.  Historical  Introduction  and  Problem .  i 

II.  Apparatus .  14 

III.  Experiments  with  Language  Materials .  16 

IV.  On  Methods  of  Learning  and  Testing  Nonsense  Syllables  .  25 

V.  Experiments  with  Plane  Areas  .  27 

1.  Adding  Variations  to  a  Material  Containing  in  Itself  Little 

Variation .  27 

2.  Adding  Variations  to  More  Varied  Materials .  34 

3.  Methods  Employed  by  the  Subjects  in  Learning  the  Series .  46 

4.  Analysis  of  Errors .  51 

5.  Other  Experiments  with  the  Same  Bases .  54 

6.  Analysis  of  Errors .  61 

VI.  Individual  Differences  in  Speed  of  Memorizing  and  in  Retentiveness  63 

VIE  Experiments  to  Determine  the  Value  of  Arranging .  65 

VIII.  Conclusion .  68 

IX.  Appendix .  74 

1.  Plates .  74 

2.  Description  of  Series .  74 

3.  Analysis  of  Errors  in  V  2 .  80 


ON  THE  INFLUENCE  OF  COMPLEXITY  AND  DIS¬ 
SIMILARITY  ON  MEMORY 

Harvey  Andrew  Peterson 

I.  HISTORICAL  INTRODUCTION  AND  PROBLEM 

The  question  of  the  relative  persistence  in  memory  of  differ¬ 
ent  kinds  of  materials  has  been  worked  out  to  a  considerable 
extent.  It  is  known  that  words  in  the  form  of  connected  pas¬ 
sages  are  vastly  better  retained  than  an  equal  number  of  dis¬ 
connected  words  or  phrases;  and  that  objects,  actions  and 
pictures  are  better  retained  than  their  verbal  equivalents.  Num¬ 
bers  and  abstract  words  belong  to  the  third  stage  of  difficulty, 
while  nonsense  syllables  are  the  most  elusive  and  most  quickly 
forgotten  of  all  materials  commonly  used  for  experimentation. 
Presentation  of  the  materials  to  several  senses  is  more  effective 
than  presentation  to  one  only.  Up  to  a  certain  stage— where 
the  limit  is  we  do  not  know — complex  material  is  retained  better 
than  that  which  is  simpler;  and  recurrent  similarity  in  the 
presentations  of  series  otherwise  different  is  disastrous.  Why 
all  this  should  be  true  is  not  so  easy  to  find  out.  There  has 
been  little  attempt  to  seek  explanatory  principles  which  would 
unify  these  diverse  facts.  The  relations  of  complexity  and 
similarity  are  both  intricate  and  close.  It  is  believed  that  a 
comprehension  of  their  relations  will  afford  a  unifying  principle 
for  some  of  the  other  facts  we  have  enumerated.  These  rela¬ 
tions  are  apparently  somewhat  as  follows,  so  far  as  they  have 
been  worked  out.  We  may  first  take  complexity. 

A  thing  is  complex  when  it  has  many  parts  and  the  parts 
have  many  interrelations,  that  is,  the  whole  has  a  high  degree 
of  organization.  A  telephone  exchange  is  complex  when  in 
operation,  while  a  corresponding  quantity  of  wire,  colored 
glass  and  electricity  is  simple  because  unorganized.  But  the 


2 


HARVET  ANDREW  PETERSON. 


fewer  the  parts  the  simpler  the  whole  because  the  possibilities 
of  interrelation  are  less. 

Complexity  affects  the  memory  through  interest  and  atten¬ 
tion.  The  simple  is  easily  mastered.  The  parts  and  their 
relations  are  few  and  the  content  is  soon  exhausted.  The 
complex,  provided  it  is  not  too  far  beyond  us,  whets  our  curios¬ 
ity.  It  gets  the  attention  and  the  thing  is  in  so  far  better 
remembered,  because  it  stays  in  consciousness  long  enough  to 
make  a  deep  impression.  But  the  complex  has  a  superiority 
in  recall  as  well  as  in  presentation,  because  of  the  high  degree 
of  organization.  This  makes  it  a  unity.  One  part  brings 
others.  A  general  idea  of  the  whole  is  also  a  very  effective 
starting  point  for  recall.  We  pass  to  the  experimental  litera¬ 
ture. 

Meakin  demonstrated  the  superior  persistence  of  the  com¬ 
plex  over  the  simple  in  passive  attention.^  He  exposed  a  line 
and  an  angle  together  for  five  seconds  directing  the  subject 
looking  at  them  to  divide  the  time  equally  between  them.  As 
soon  as  the  exposure  was  over  the  subject  closed  his  eyes  and 
remained  passive  for  sixty  seconds  reporting  the  entrance  and 
exit  of  the  two  images.  The  angles  were  in  consciousness  an 
average  of  38  seconds;  the  lines,  32  seconds.  In  the  same  way 
he  compared  plain  figures  and  identical  figures  with  concentric 
lines  just  inside  the  periphery,  plain  and  identical  colored 
figures,  and  figures  of  less  and  of  more  complex  outlines.  His 
resultswere,  for  the  plain  and  the  marked,  24  and  37  seconds; 
for  the  plain  and  the  colored,  31  and  38  seconds;  for  the  simple 
and  the  complex  outlines,  27  and  35  seconds. 

Binet  and  Henri  compared  the  memory  of  school  children 
for  disconnected  words  and  for  sentences,  the  material  being 
read  to  the  children.^  Although  the  comparison  was  not  car¬ 
ried  further  than  lists  of  seven  or  eight  words,  it  was  found 
that  about  twenty-five  times  as  many  words  were  recalled  from 
the  sentences  as  from  the  lists  containing  equal  numbers  of 
words.  The  reproduction  was  immediate.  Mere  connecting 
words  in  the  sentences  were  disregarded. 

^  Psych.  Rev.,  1903,  Mon.  Sup.,  no.  4,  p.  235. 

^  Binet  and  Henri:  L’Annee  Psych.,  1894,  I,  1-59. 


INFLUENCE  OF  COMPLEXITF  AND  DISSIMILARITY  ON  MEMORY. 


3 


Dr.  Gordon  introduced  a  novelty  into  memory  work  when 
she  made  the  complex  material  consist  of  combinations  wholly 
unfamiliar  to  the  subject.^  This  property  cannot  be  claimed 
in  toto  for  sentences,  since  the  past  experiences  of  the  listener 
render  them  a  unity  to  some  extent,  even  before  they  are  heard. 
Dr.  Gordon’s  simple  material  consisted  of  series  of  nonsense 
syllables,  nine  in  a  series,  shown  through  a  single  aperture. 
With  this  she  contrasted  three  types  of  complex  series  in  the 
first  of  which  each  syllable  had  a  background  of  a  different 
color.  In  a  second  type  the  syllables  were  black  like  the  sim¬ 
ple  type,  but  were  shown  through  nine  apertures  distributed 
around  the  periphery  of  the  screen;  thus  each  syllable  had  a 
distinctive  spatial  position.  In  a  third  type  the  backgrounds 
were  colored  and  the  positions  were  also  changed,  the 
apertures  forming  a  vertical  column  in  the  middle  of  the 
screen.  The  standard  of  measurement  was  the  number  of 
repetitions  required  for  complete  learning,  and  relearning  after 
a  day,  and  in  the  test  the  question  was  not  how  many  of  the 
combinations  of  color,  position  and  syllable  can  the  subject 
recall,  but  merely  how  many  syllables  can  be  recalled.  The 
novelty  of  the  experiment  consisted  in  the  expectation  that  the 
secondary  associations  of  syllable  with  color  and  position  would 
be  formed  during  the  brief  period  of  learning.  Unquestionably 
these  complex  series  were  at  a  disadvantage  compared  with 
the  simple  series  because  of  the  burden  thus  imposed,  but  on 
the  other  hand  in  recall  they  possessed  the  theoretical  advan¬ 
tage  of  furnishing  the  subject  with  more  recall  cues,  namely, 
the  color  and  the  spatial  location  of  the  syllables.  Kuhlmann 
has  5hown,  what  was  suspected  before,  that  spatial  location  is 
one  of  the  most  easily  formed  and  most  lasting  associations. ^ 
The  principle  involved  has  been  stated  by  James,  that  other 
things  being  equal,  the  chances  of  a  fact  being  recalled  are  in 
proportion  to  the  number  of  connections  between  it  and  the 
rest  of  our  experience.^  The  results  of  the  Gordon  experiment 
showed  a  decided  advantage  for  the  complex  series.  The  fig- 

*  Gordon,  K.:  Meaningin  Memory  and  Attention.  Psych.  Rev.,  1903, X,  267. 

*  Kuhlmann,  F. :  Psych.  Rev.,  1906,  XIII,  321. 

^  James:  Principles  of  Psychology,  I,  661. 


4 


HARVEY  ANDREW  PETERSON. 


ures  give  the  average  number  of  repetitions  required  for  learn¬ 
ing  and  relearning. 


First  Second 

learning  learning 


Plain  syllables  shown  in  one  place .  7  °5  4.06 

Plain  syllables  shown  in  nine  places .  6.60  3-^3 

Plain  syllables  shown  in  one  place .  6.04  3 -40 

Colored  syllables  shown  in  one  place .  2.79 

Colored  syllables  shown  in  nine  places .  5-^7  3-26 


Dr.  Gordon  suggested  that  the  advantage  of  increasing  the 
complexity  in  this  way  would  soon  reach  a  limit,  where  more 
potential  clues  would  be  offered  than  the  learner  could  use  in 
so  short  a  time  of  learning,  and  where  distraction  would  begin 
to  operate.  It  is  the  main  problem  of  the  present  Investigation 
to  find  these  limits  in  a  few  typical  cases. 

If  the  mind  loves  complexity  somewhat,  it  loves  variety  and 
change  at  least  as  much, — common  sense  would  unhesitatingly 
say,  more, — and  here  again  it  is  through  the  superior  hold 
which  variety  has  on  our  attention  and  interest  that  the  memory 
is  improved.  Let  us  first  distinguish  the  pair,  variety  and 
sameness  (or  similarity),  from  complexity  and  simplicity;  for 
though  they  have  much  in  common  they  are  not  identical.  Two 
things  are  varied  when  oneismoreor  less  different  from  the  other, 
has  something  not  contained  in  the  other.  It  is  true  that  variety 
presupposes  complexity,  for  without  a  plurality  of  parts  and 
relations  some  of  which  are  now  included  and  now  left  out, 
variety  is  impossible.  But  the  converse  is  not  true,  for  the 
same  complex  may  recur  without  affording  much  variety.  The 
simple  usually  has  sameness  about  it,  though  it  may  have  that 
low  order  of  variety  which  comes  from  a  mere  change  of  parts, 
as  when  one  changes  from  a  collection  of  colors  to  one  of  letters. 
There  is  little  complexity  in  either  because  of  the  relative 
absence  of  organization.  The  distinction  which  will  be  signifi¬ 
cant  for  the  present  investigation  is  the  fact  that  one  might  in¬ 
crease  the  complexity  without  necessarily  increasing  the  variety. 
It  is  the  varied  complexity  which  in  our  opinion  seems  fruitful 
for  memory  and  which  the  present  investigation  is  concerned 
with. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  5 


The  beneficial  effect  of  considerable  variety  upon  memory  is 
a  commonplace.  A  speaker  who  uses  only  a  few  tones  is  at  a 
disadvantage  compared  with  one  who  uses  intonation  properly. 
School  programs  rotate  their  studies  with  an  eye  to  variety,  and 
not  only  interest  but  memory  directly  profits  by  the  change. 
Much  of  the  bad  effect  of  prolonged  sameness  in  work  is  trace¬ 
able  to  fatigue,  but  not  all,  as  we  shall  see.  All  memory  is 
associative.  There  is  no  such  thing  as  memorizing  things 
without  relating  them.  With  prolonged  sameness  or  similarity 
the  associations  derived  from  a  presented  material,  quite  apart 
from  fatigue,  become  confused  with  one  another,  jumbling 
begins,  and  the  memory  weakens,  unable  to  straighten  out  the 
tangle  of  similarities.  On  the  contrary  the  dissimilar  are  much 
more  easily  kept  apart,  and  fatigue  is  less. 

In  the  experimental  investigations  variety  is  quite  commonly 
spoken  of  as  vividness.  Miss  Calkins’  investigation  is  well 
known. ^  Numbers  were  associated  with  colors  in  couplets, 
twelve  couplets  constituting  a  series.  To  speak  first  only  of 
the  vividness  experiments  proper,  all  the  numbers  in  a  series 
except  one  were  black  two-place  numbers,  the  one  remaining 
was  a  three-place  number  or  had  red  figures,  or  was  differen¬ 
tiated  qualitatively  from  the  others  by  some  other  similar  means. 
One  of  the  ordinary  numbers  was  associated  with  the  same 
color  as  the  vivid  number.  Thus  the  series  of  twelve  couplets 
consisted  of  ten  ordinary  couplets,  one  critical  couplet,  and  one 
so-called  normal  couplet  which  competed  with  the  critical  in 
recall.  The  ordinary  and  normal  couplets  were  two  different 
standards  of  comparison  for  the  critical  pairs.  In  the  test  for 
immediate  recall  the  subject  was  shown  the  colors  in  altered 
order  and  was  asked  to  give  the  numbers  which  had  been 
shown  with  each.  The  repeated  color  was  shown  only  once. 
It  might  recall  the  vivid  number  alone,  or  both  the  vivid  and 
the  normal  number,  or  the  normal  alone.  The  vivid  number 
was  recalled  52  per  cent  of  the  possible  number  of  cases,  the 
normal  21  per  cent,  while  the  general  average  of  recall  for  the 
ordinary  combinations  of  all  the  series  was  26  per  cent.  Thus 

'  Calkins,  M.  W.:  Association,  Psych.  Rev.,  1896,  Mon.  Sup.,  no.  i. 


6 


HARVEr  ANDREW  PETERSON. 


we  have  a  measure  of  the  effectiveness  of /A/j-  kind  of  vividness. ‘ 
In  other  experiments  the  critical  number  was  the  same  as  the 
rest  of  the  series  in  all  respects  save  that  it  was  repeated  three 
times.  This  measured  the  effectiveness  of  repetition.  In  a 
similar  way  other  experiments  tested  the  worth  of  the  first  and 
last  positions  in  the  series  (primacy  and  recency).  All  four 
kinds  of  critical  couplets  were  superior  in  recall  to  the  ordinary 
and  the  normal  combinations  by  varying  amounts. 

The  analysis  of  the  relations  of  sameness  and  variety  made 
in  the  preceding  pages  leads  us  to  an  interpretation  of  this 
experiment  which  is  quite  different  from  that  of  Miss  Calkins. 
Just  because  there  was  only  one  of  the  critical  pairs  while  there 
were  eight  or  ten  of  the  ordinary  pairs  in  a  series,  all  four  types 
of  experiments  (vividness,  frequency,  recency  and  primacy)  are 
studies  in  the  effect  of  variety.  All  four  of  the  critical  couplets 
are  a  change  from  the  sameness  of  the  other  couplets  of  the 
series.  The  superiority  of  the  frequent  couplet  for  example 
is  due  in  some  measure  to  the  fact  of  its  repetition.  But  its 
superiority  is  due  quite  as  much  and  perhaps  more  to  the  fact, 
already  mentioned,  that  the  other  couplets  of  the  series  are  all 
pretty  much  alike,  while  the  frequent  couplet  affords  a  change, 
amid  sameness.  It  is  extremely  probable  that  if  the  relations 
were  reversed,  the  mass  of  the  series  being  given  the  threefold 
repetition  and  the  critical  couplet  being  given  only  once, 
the  critical  couplet  would  still  be  better  remembered,  providing 
that  the  subject  knew  which  was  the  critical  couplet  when  he 
saw  it.^  In  the  experiments  of  Miss  Calkins  on  frequency  the 
second  repetition  of  the  critical  couplet  furnished  this  clue. 
The  isolation  of  the  frequency  factor  from  the  sameness-variety 
factor  could  be  secured  only  by  repeating  one-half  of  the  series 
a  larger  number  of  times  than  the  other  half.^ 

'  The  italics  are  ours. 

^  “It  is  not  the  mere  intensity  of  the  stimulus  which  is  effective  in  attracting 
the  attention  so  much  as  it  is  the  change  in  intensity.  ...  A  negative 
change  will  have  the  same  general  effect.”  Pillsbury:  Attention,  pp.  28-29. 
I'he  same  is  true  of  memory  to  a  less  extent. 

^  The  question  has  been  worked  out  with  nonsense  syllables  in  the  form  of 
the  worth  of  the  individual  repetitions.  Cf.  Ebbinghaus:  Grundztige.d.  Psychol.. 
1,  p.  652.  Zweite  .Aiiflage. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  J 


Take  next  the  results  on  primacy.  Suppose  that  the  length 
of  the  series  had  been  three  couplets  instead  of  twelve,  and  that 
the  color  which  had  stood  in  the  first  place  had  been  repeated 
in  the  middle  place  with  a  different  number:  Would  primacy 
have  been  worth  any  more  than  normal  (here  the  middle) 
Probably  not.  Then  primacy  is  purely  another  form  of  vivid¬ 
ness.  There  is  no  other  factor  involved,  as  there  was  in  the 
frequency  case.  The  experiments  on  recency  involve  two  fac¬ 
tors,  recency  and  sameness-variety.  The  worth  of  the  former 
is  attested  by  the  fact  that  in  memory  work  in  general  the 
terms  just  preceding  the  last  are  better  recalled  than  their  im¬ 
mediate  predecessors.  But  the  last  term  is  so  very  much  better 
recalled  than  the  term  just  preceding  it  (which  is  almost  as 
recent),  that  the  sameness-variety  factor  is  much  the  larger  one.^ 
To  summarize  the  foregoing  criticism,  frequency  and  recency 
improve  the  memory  apart  from  the  question  of  sameness  and 
variety.  Vividness  and  primacy  are  simply  species  of  variety. 
But  the  fewness  of  all  the  critical  combinations  compared  with 
the  large  number  of  ordinary  combinations  gives  the  critical 
ones  the  advantage  which  comes  from  a  change  from  the  rou¬ 
tine,  and  in  view  of  the  greatness  of  the  numerical  disparity, 
the  whole  investigation  is  a  study  mainly  of  different  forms  of 
vividness  or,  in  our  own  terms,  of  variety.^ 

Aside  from  Miss  Calkins’  investigation,  and  the  one  by  Dr. 
Gordon  already  described  (which  may  be  viewed  as  an  experi- 

^  Cf.  Ebbinghaus:  Op.  cit.,  p.  653.  Muller  and  Pilzecker:  Ztsch.  f.  Psych., 
1900,  Ergdtizungsbd.  I,  p.  264. 

^  It  is  significant  that  the  percentages  of  recall  for  the  normal  numbers  were 
usually  less  than  that  of  the  ordinary  combinations.  The  fact  is  another  illus¬ 
tration  of  the  disastrous  effects  of  similarity.  The  critical  color  and  the  normal 
number  together  are  similar  to  the  same  color  and  the  unusual  number  taken 
together.  If  ab  be  stands  for  these  two  couplets  respectively,  given  b  (the 
common  color),  a  has  by  no  means  as  Titchener  says  {Experimental  Psychology, 
vol.  I,  pt.  II,  p.  407)  “a  chance  equal  to  that  of  the  other  terms  of  the  series,” 
for  it  is  interfered  wdth  by  a  competing  association,  be.  For  the  same  reason 
the  figures  given  for  vividness,  frequency,  etc.,  in  so  far  underestimate  the  value 
of  the  factors  since  interference  is  always  mutual.  Of  course  the  factor  of 
dissimilarity  contained  in  them  much  overbalances  the  interference. 


8 


HARVEY  ANDREW  PETERSON. 


ment  either  in  variety  or  in  complexity^)  the  writer  is  not 
aware  of  other  experiments  on  the  positive  effects  of  variety. 
There  are  however  a  number  of  important  and  extended 
researches  on  the  negative  side,  namely,  the  injurious  effects  of 
increasing  similarity  of  associations,  in  comparison  with  which 
the  material  free  from  the  similarity  is  relatively  varied. 

Muller  and  Schumann  found  that  syllables  which  had  been 
used  once  in  old  series  were  more  difficult  to  learn  in  new  series 
than  syllables  which  had  not  been  used  before.^  The  old  asso¬ 
ciates  either  appeared  in  consciousness  and  hindered  the  forma¬ 
tion  of  the  new  connections,  or  there  was  a  purely  physiological 
interference  manifested  by  the  poorer  recall.  Here  the  old 
series  and  the  series  in  which  they  were  used  again  constitute 
together  the  less  varied  material,  while  the  series  not  re-used 
are  the  more  varied  material. 

Muller  and  Pilzecker  made  an  exhaustive  study  of  interfer¬ 
ence  using  nonsense  syllables.^  These  experimenters  demon¬ 
strated  that  in  the  case  of  two  associations  of  the  type  ab  be 
the  interference  is  mutual.  Their  method  was  in  principle  the 
same  as  that  of  Muller  and  Schumann,  except  that  they  em¬ 
ployed  the  method  of  successes.  Each  day  the  subject  learned 
four  antecedent  series  and  an  equal  number  of  sequent  series. 
The  antecedent  series  were  normally  constructed  eight-syl¬ 
lable  series.  They  were  read  in  trochaic  rhythm,  hence  each 
series  fell  into  four  feet,  a  foot  containing  an  accented  and  an 
unaccented  syllable.  The  series  were  given  a  fixed  number  of 
repetitions  and  in  the  recall  (to  come  later)  the  subject  was 
given  the  accented  syllables  in  altered  order  and  asked  to  give 
the  unaccented  ones  which  had  accompanied  each.  After 

‘  Because  the  increase  was  in  the  direction  of  dissimilar  complexity.  The 
spatial  positions  and  the  colors  which  were  added  to  the  syllables  were  them¬ 
selves  varied. 

^  Muller  and  Schumann:  Exp.  Beitrage  zur  Untersuchung  des  Gedachtnisses. 
Ztsch.  f.  Psych.,  1894,  6:177  and  318.  Also  Muller  and  Pilzecker,  who  on 
p.  83  in  the  work  referred  to  in  the  following  note  summarize  Muller  and  Schu¬ 
mann’s  results. 

^  Muller  and  Pilzecker:  Exp.  Beitrage  zur  Lehre  vom  Gedachtniss.  Ztsch. 
f.  Psych.,  1900,  Erganzungsbd.  L 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  9 

learning  the  four  antecedent  series  the  subject  was  given  the 
four  sequent  series.  These  were  formed  by  combining  two  of 
the  accented  syllables  of  the  antecedent  series  with  new  unac¬ 
cented  syllables.  This  furnished  two  of  the  four  feet,  and  the 
other  two  were  made  of  new  syllables.  The  series  may  be 
symbolized  thus: 

Antecedent  series:  ah  cd  ei  gh. 

Sequent  series:  ij  ak  Im  ^n. 

After  learning  the  four  antecedent  and  first  sequent  series  the 
subject  was  tested  on  the  first  antecedent  and  the  first  sequent 
series.  Then  followed  the  learning  of  the  second  sequent  series 
and  the  second  pair  of  tests,  and  so  on  till  all  eight  series  had 
been  learned  and  tested.  The  half  of  the  couplets  represented 
by  the  letters  cd,  gh,  ij,  and  Im  may  be  called  the  normal  coup¬ 
lets;  the  other  half,  ab,  ef,  ak,  and  en,  the  interference  couplets. 
The  former  Were  simply  a  standard  with  which  the  interference 
in  the  latter  might  be  compared.  When  the  antecedent  series 
was  tested  (by  giving  a,  c,  e,  and  g),  k  and  n  interfered  with 
the  recall  of  b  and  f.  When  the  sequent  series  was  tested  (by 
giving  i,  a,  1  and  e),  b  and  f  interfered  with  the  recall  of  k  and 
n.  The  following  are  typical  results. 

Percentage  of  Correct  Recalls. 

(Number  of  couplets  i68) 

Per  cent 


Normal  Couplets,  Antecedent  Series .  66 

Interference  Couplets  of  same . 

Normal  Couplets,  Sequent  Series .  63.5 

Interference  Couplets  of  same .  52  -5 


The  next  day  the  tests  were  repeated  and  the  relations  of 
the  two  interference  groups  to  their  respective  standards  were 
found  to  be  reversed.  It  was  now  the  sequent  series  which 
showed  by  far  the  greater  loss.  This  reversal  is  a  study  in  the 
effects  of  recency,  into  which  it  is  beside  our  purpose  to  go.^ 

‘  While  the  second  learnings  were  still  fresh  in  mind  a  and  e  suggested  their 
second  associates  without  much  difficulty.  But  when  the  tests  were  put  off  or 
repeated  later,  the  first  associates  became  the  stronger. 


10 


HARVET  ANDREW  PETERSON. 


The  extent  to  which  the  interference  might  go  may  be  seen  in 
the  fact  that  in  some  cases  the  interference  recall  in  both  ante¬ 
cedent  and  sequent  series  together  was  less  than  the  normal 
recall  of  the  antecedent  series. 

It  is  probably  unnecessary  to  point  out  the  relevancy  of  these 
experiments  to  the  question  of  the  effects  of  similarity  and 
variety  upon  memory.  The  normal  couplets  are  relatively  a 
more  varied  material  than  the  interference  couplets.  While 
the  sameness  in  the  latter  is  planned  with  malice  aforethought, 
so  to  speak,  the  same  thing  happens  in  daily  experience  where 
the  sameness  is  unintentional,  and  not  so  exactly  measured. 
The  experiments  of  Ranschburg  with  numbers,  described  below, 
illustrate  how  daily  experience  is  full  of  the  ab  be  type  of 
similarity. 

Ranschburg  has  confirmed  the  results  of  Muller  and  Pil- 
zecker  and  Muller  and  Schumann. ‘  Most  of  the  details  are 
omitted  here  because  of  their  similarity  to  the  two  works  last 
described.  Using  the  method  of  successes  this  author  arranged 
what  he  calls  heterogeneous  and  homogeneous  series.  The 
heterogeneous  were  simply  normal  eight-syllable  series.  Of 
the  homogeneous  the  first  series  was  also  normal,  but  the  rest 
were  not,  for  they  were  all  identical  with  the  first  in  respect  to 
their  consonants.  Only  the  vowels  were  changed  in  each  suc¬ 
ceeding  series.  These  two  kinds  of  series  were  learned  in 
parallel  fashion.  The  confusing  result  may  be  imagined, 
especially  when  an  accumulation  of  eight  series  of  each  kind, 
the  learning  of  which  had  extended  over  a  number  of  days, 
was  given  a  few  renewing  repetitions  and  then  tested  “run 
together.”  His  experiments  with  words  are  somewhat  newer. 
In  these  latter  various  series  of  word-couplets  were  devised  in 
which  the  words  in  a  couplet  were  closely  germane  in  thought, 
but  the  couplets  were  drawn  from  quite  disparate  thought  uni¬ 
verses.  In  other  series  the  couplets  were  internally  as  before, 
but  several  couplets  were  drawn  from  similar  and  in  some 
cases  practically  the  same  thought  universes.  The  similarity 

^  Ranschburg.  P. :  Ueber  die  Bedeutung  der  Aehnlichkeit  beim  Erlernen, 
Behalten,  und  bei  der  Reproduction.  J.  f.  Psych,  u.  Neur.,  1905,  5:93. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  1 1 


was  entirely  on  the  side  of  thought.  In  recall  the  subject  was 
very  much  more  certain  of  the  dissimilar  series,  and  the  per¬ 
centages  of  recall  were  much  higher  than  in  the  similar  series. 
In  the  latter  the  subject  was  quite  apt  to  hesitate  between  the 
correct  response  and  a  word  in  another  couplet  which  was 
similar  in  meaning,  but  might  be  quite  removed  in  the  time  of 
learning. 

In  another  investigation  on  the  conditions  of  perception  of 
similar  and  dissimilar  numbers  Ranschburg  showed  that  the 
fusion  of  similar  things  which  we  have  seen  taking  place  in 
memory  exists  even  in  the  perception,  when  the  time  of  expo¬ 
sure  is  short. ^  Indeed  he  traces  the  memory  confusion  back 
to  perceptual  confusion,  in  cases  where  the  successive  presen¬ 
tations  possess  considerable  similarity.  The  experiment  is  for 
this  reason  relevant  to  our  problem:  it  offers  an  explanation  for 
a  considerable  part  of  the  interference  in  similar  memory 
material.  It  is  also  important  for  our  problem  because  it 
endeavors  to  measure  the  degree  of  interference  due  to  inherent 
similarity,  and  not  to  the  fact  that  the  associations  were  made 
to  interfere.  In  experimenting  upon  the  span  and  accuracy  of 
visual  perception,  using  six-place  numbers  exposed  one-third 
of  a  second,  Ranschburg  observed  that  a  large  proportion  of 
the  errors  were  traceable  to  the  inherent  similarity  of  certain 
figures,  for  example  6,  9,  and  o,  3  and  8,  9  and  2,  1,4,  and  7. 
He  was  able  to  determine  the  nature  of  the  errors  with  con¬ 
siderable  certainty  because  in  nearly  all  cases  they  involved 
only  one  or  two  figures,  and  the  figures  were  nearly  always  in 
the  fourth  or  fifth  positions,  less  often  in  the  third,  from  the 
left.  Where  only  one  figure  was  wrong,  it  belonged  in  nearly 
every  case  to  one  of  the  five  following  types:  (i)  Substitution  of 
a  similar  reproduced  number,  e.  g.,  an  8  for  a  3;  (2)  assimila¬ 
tion  to  a  similar  nearby  figure,  e.  g.,  684223  instead  of  684293; 
(3)  assimilation  to  a  dissimilar  nearby  figure,  e.  g.,  162445 
instead  of  i62<?45;  (4)  change  of  one  of  two  identical  figures  to 
any  other  figure;  (5)  substitution  of  a  figure  either  preferred  for 

^  Ranschburg:  Ueber  Hemmung  Gleichzeitiger  Reizwirkungen.  Ztsch.  f. 
Psych.,  1902,  30:39. 


12 


HARVEY  ANDREW  PETERSON. 


some  temperamental  reason  or  connected  closely  in  experience 
with  the  given  figure.  The  fifth  seldom  occurred.  Where  two 
figures  were  wrong  nearly  all  the  cases  were  either  simple  inver¬ 
sion  (78  instead  of  87)  or  a  combination  of  inversion  with  one 
of  the  types  enumerated  above.  The  first  four  classes  of  errors 
are  types  of  similarity.  The  fifth  and  inversion  are  not.  The 
large  proportion  of  similarity  errors  makes  it  highly  improbable 
that  they  are  due  to  chance. 

In  the  light  of  this  statistical  analysis  of  the  errors  in  num¬ 
bers  not  devised  to  test  similarity,  but  cut  from  a  statistical 
handbook,  he  constructed  numbers  of  several  different  kinds 
of  similarity  for  the  purpose  of  finding  out  whether  “the 
threshhold  of  perception  is  higher  for  homogeneous  than  for 
heterogeneous  material.”  In  the  first  experiment  he  gave  in 
the  same  way  as  before  20  six-place  numbers  lacking  similarity 
internally,  and  20  six-place  numbers  two  figures  of  which, 
usually  in  the  right  part  of  the  series,  were  identical,  e.  g., 
1 19495,  or  141993.  In  a  second  experiment  the  critical  figures 
were  only  similar.  The  results  confirmed  his  hypothesis. 
Where  two  of  the  figures  were  similar,  the  errors  were  about 
three  times  as  great  as  in  the  dissimilar  numbers,  but  where 
two  figures  were  identical,  the  errors  were  four  times  as  great 
as  in  the  dissimilar  numbers.  The  threshold  of  perception  is 
therefore  higher  in  proportion  to  the  similarity.  These  figures 
are  valuable  because  they  are  among  the  few,  to  the  writer’s 
knowledge,  in  which  the  amount  of  visual  similarity  is  con¬ 
trolled.  Whether  they  bear  upon  the  effects  of  similarity  on 
memory  is  another  question.  There  is  no  objection  to  viewing 
the  responses  of  the  subjects  as  immediate  recall,  providing  the 
conditions  of  exposure  are  comparable  to  the  conditions  of 
exposure  in  memory  work.  It  may  be  said  that  in  memory 
tests  the  subject  is  assured  of  a  long  enough  interval  to  prop¬ 
erly  perceive  the  material.  But  it  may  be  quite  fairly  said  in 
reply  that  while  the  absolute  exposure  is  usually  much  longer 
than  was  used  here,  the  adequacy  of  it  to  distinguish  the  terms 
from  each  other  depends  upon  their  similarity.  I  should  say 
that  the  conditions  are  comparable  to  those  in  memory  in 
many  cases.  On  the  other  hand  the  confusion  in  such  experi- 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  13 

merits  as  those  of  Muller  and  Pilzecker  are  not  confusions  in 
perception  but  in  memoryd 

To  summarize  the  various  investigations  of  the  influence  of 
relative  sameness  and  variety  on  memory:  anything  which 
serves  to  distinguish  a  thing  from  a  group  makes  it  better 
remembered.  A  greater  length,  a  different  color,  a  more  fre¬ 
quent  repetition,  an  unusual  position  spatially  or  temporally 
are  some  of  the  variations  which  have  been  shown  to  be  effect¬ 
ive.  Where  the  similarity  results  from  the  triangular  associa¬ 
tion  of  two  things  with  a  third,  if  the  recall  proceeds  from  the 
common  element  towards  one  of  the  extremes,  the  other  extreme 
interferes  and  diminishes  the  chances  of  recall.  The  result  is 
the  same  if  the  start  be  made  toward  the  other  extreme.  The 
conflict  may  be  purely  physiological,  and  apparent  in  conscious¬ 
ness  only  as  a  delayed  recall.  The  injurious  effects  of  simi¬ 
larity  are  however  not  confined  to  artificially  constructed  over¬ 
lapping  associations,  but  also  occur  where  the  similarity  is 
inherent  in  the  nature  of  the  material.  In  contrast  with  this, 
wherever  the  different  parts  of  the  material  learned  are  dis¬ 
similar,  the  associations  are  more  lasting  and  their  recall  pro¬ 
ceeds  more  promptly,  because  they  do  not  interfere  with  one 
another.  It  has  also  been  shown  that  the  threshold  of  per¬ 
ception  is  higher  for  similar  material  than  for  dissimilar.  It 
requires  a  longer  time  to  get  a  clear  perception  of  a  material 
the  parts  of  which  are  similar  than  it  does  of  one  the  parts  of 
which  are  not  similar.  The  differentiation  here  referred  to  is 
however  purely  involuntary  and  almost  instantaneous.  If  the 
perceiving  process  is  cut  off  before  clearness  has  been  reached, 

^  Other  experiments  on  the  effects  of  similarity  on  memory  are  those  of  Berg¬ 
strom  on  the  interference  arising  from  sorting  the  same  cards  into  different 
arrangements  of  the  same  positions,  in  Am.  Jour,  of  Psych.,  1893,  V,  356,  and 
1894,  VI,  432.  Also  Miinsterberg,  in  Beitrage  zur  Exp.  Psych.,  Heft  4,  p. 
69.  Both  of  these  deal  with  the  interference  of  automatic  habits  of  movement. 
The  latter  shows  how  opposed  habits,  after  being  made  automatic  separately, 
may  be  used  for  alternate  periods  of  considerable  length  without  interference, 
e.  g.,  keeping  one’s  watch  first  in  one  pocket  and  then  in  another,  the  same  arm 
being  used  for  both  movements.  It  certainly  offers  something  for  reconcilia¬ 
tion  with  the  otherwise  uniform  outcome  of  the  similarity  literature. 


HARVEY  ANDREW  PETERSON. 


14 

the  errors  in  recall  are  largely  of  the  type  of  confusion  of  sim¬ 
ilars. 

Summarizing  the  influence  of  complexity  on  memory  we 
may  say:  the  complexity  afforded  the  mind  by  sentences  or 
connected  passages  is  superior  to  the  simplicity  of  disconnected 
words  because  of  the  unity  of  the  whole  passage  and  the  result¬ 
ing  greater  differentiation  of  the  parts.  In  assimilating  a 
simple  linguistic  material  such  as  nonsense  syllables,  letters  or 
even  disconnected  words,  a  person  not  only  tries  to  give  it  a 
unity  by  connecting  it  with  his  experience,  but  also  seeks  dif¬ 
ferentials  by  which  to  distinguish  the  parts;  and  in  the  absence 
of  preformed  associations  which  may  serve  the  purpose  (for 
example  the  English  words  suggested  by  nonsense  syllables), 
any  peculiarity  such  as  spatial  location,  background,  etc,,  will 
be  utilized.  But  the  peculiarities  thus  utilized  are  increases  in 
complexity.  In  these  cases  the  secondary  associations  (loca¬ 
tion,  background,  etc.)  are  formed  during  the  memorizing  of 
the  principal  associations. 

We  are  thus  brought  to  the  problem  of  the  present  investi¬ 
gation.  Two  factors  are  involved  which  are  inversely  related 
to  each  other.  Increasing  the  complexity  diminishes  the  simi¬ 
larity,  and  this  is  favorable  to  memorizing.  On  the  other 
hand,  if  the  material  is  not  a  unity  in  advance,  complexity 
increases  the  association  processes,  the  mental  effort  presumably 
required,  and  consequently  the  possibilities  of  distraction. 
Under  these  conditions  how  much  will  variation  added  to  a 
material,  highly  similar  in  itself,  shorten  the  learning  time  and 
improve  the  retention  I  Is  there  a  resulting  profit  to  the  mem¬ 
ory  only  when  the  original  material  is  highly  similar,  or  may 
it  possess  considerable  variety  ?  When  does  distraction  enter  ? 
Is  there  a  relation  between  the  amount  of  complexity  which  a 
person  will  make  use  of  and  his  retentiveness  ? 

II.  APPARATUS 

With  slight  changes  the  same  apparatus  was  used  throughout 
the  investigation.  The  essential  part  was  an  electro-magnetic 
shutter  which  by  its  movements  opened  and  closed  a  small 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  15 

r 

aperture  in  a  screen.  The  screen  was  2  m.  ii  cm.  long  and 
58  cm.  high.  Near  the  middle  was  an  aperture  9.5  cm.  wide 
and  2  cm.  high.  The  subject  sat  in  front  of  the  screen,  and 
when  he  looked  at  a  series  he  brought  his  eyes  within  about 
3  cm.  of  the  aperture.  Behind  the  screen,  74  cm.  from  it  and 
parallel  to  it,  was  a  track  somewhat  longer  than  the  screen, 
supported  by  adjustable  standards,  and  carrying  a  car  i  m. 
long  and  ii  cm.  wide.  On  the  floor  of  the  car  and  running 
the  length  of  it  was  a  groove,  into  which  any  kind  of  series 


The  apparatus  is  described  in  the  text.  A  is  aperture;  E  S,  electro-mag¬ 
netic  shutter;  T,  track;  fF S,  wide  screen;  C,  car;  A  S,  adjustable  screens;  L  S, 
lower  screen;  S,  shunt;  M  B,  metronome  box;  R  B,  rubber  bands,  upper  and 
lower,  which  limit  the  play  of  the  shutter. 

mounted  on  heavy  cardboard  could  be  slid  preparatory  to 
exposing  it.  On  the  back  of  the  car  were  four  upright  steel 
rods  25  cm.  high  on  the  top  of  which  were  four  spring  clasps. 
Small  cardboard  flaps  on  the  back  of  the  series  when  put  into 
the  spring  clasps  held  the  series  rigidly  in  place.  Two  black 
screens  71  cm.  high  and  56  cm.  wide,  extending  from  the  large 
screen  on  the  front  of  the  tables  to  the  track,  could  be  so 
adjusted  by  the  operator  as  to  confine  the  subject’s  gaze  to  as 


1 6  HARVET  ANDREW  PETERSON. 

small  a  space  as  desired.  They  could  be  widened  so  as  to 
expose  a  whole  series  at  once.  The  car  would  of  course  then 
remain  motionless  during  exposure.  Or  they  could  be  narrowed 
to  the  width  of  a  single  term  of  a  series,  15  cm.  for  example. 
For  successive  exposure  the  car  would  then  be  moved  past 
this  space  by  the  operator  during  the  intervals  while  the  aper¬ 
ture  was  closed.  The  great  advantage  of  the  apparatus  was 
that  whenever  the  subject  was  looking  the  series  did  not  move. 
A  scale,  25  cm.  in  length  on  the  front  of  the  track,  enabled  the 
screens  to  be  quickly  adjusted  to  any  desirable  width.  The 
operator  was  cut  off  from  the  subject  by  a  strip  of  cardboard 
extending  across  the  upper  part  of  the  space  between  the  con¬ 
verging  screens.  The  essential  part  of  the  apparatus,  the  shut¬ 
ter,  remains  to  be  described.  This  consisted  of  an  iron  lever 
53  cm.  long  carrying  a  movable  counterpoise  on  the  short 
arm  and  the  shutter  on  the  end  of  the  long  arm.  An  electro¬ 
magnet  under  the  lever  drew  down  the  short  arm  when  the 
circuit  was  closed,  at  which  the  long  arm  carrying  the  shutter 
moved  up  and  closed  the  aperture.  When  the  circuit  was 
broken  a  coiled  spring  connected  with  the  wooden  base  drew 
the  arm  down  and  thus  opened  the  aperture.  The  current 
was  led  first  to  the  commutator,  then  through  the  electro¬ 
magnet  and  a  metronome.  A  small  rheostat  connected  at  the 
commutator  with  the  apparatus  furnished  a  shunt  to  the  current 
at  the  moment  when  it  was  broken  by  the  metronome.  The 
metronome,  enclosed  in  a  felt-lined  box,  regulated  the  move¬ 
ments  of  the  shutter,  while  a  small  rod  passing  through  the 
wall  of  the  box  intercepted  the  pendulum  or  set  it  free  when 
desired.  A  year’s  constant  use  of  the  apparatus  has  led  to  the 
conclusion  that  it  is  a  satisfactory  exposure  mechanism  for 
memory  work  of  this  kind. 

III.  EXPERIMENTS  WITH  LANGUAGE  MATERIALS 

The  first  effort  was  to  extend  the  experiments  of  Dr.  Gordon. 
Series  of  nonsense  syllables  of  the  length  used  by  her  (nine 
syllables)  were  varied  in  size,  color  and  style  of  type.  The  rules 
of  Muller  and  Schumann  w^ere  follow^ed  in  constructing  the 

O 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  I  7 


series.  No  syllable  was  used  twice.  The  variations  were  first 
tried  out  separately  and  later  in  combination.  Variations  in 
size  were  secured  by  using  Willson  Gummed  Letters  numbers 
I,  20,  21,  23  and  25.  The  largest  letters  were  38,  the  smallest 
7  mm.  high.  The  letters  were  all  of  heavy  type,  the  lines  of  the 
largest  being  8  mm.  thick.  Thus  a  strong  difference  in  sensation 
was  secured.  A  medium  size,  No.  21,  was  used  for  the  standard 
and  colored  series.^  Color  variationwasobtainedbypainting  white 
letters  red,  orange,  yellow,  green,  blue,  brown,  neutral  gray,  and 
black.  White  furnished  the  ninth  variation.  In  the  series  in 
which  the  size  varied  there  were  two  syllables  in  each  of  four 
sizes  and  one  in  a  fifth  size,  while  in  the  color-varying  series 
each  syllable  was  of  a  different  color  or  brightness.  Five  dif¬ 
ferent  styles  of  lettering  were  used  in  the  form-varying  series, 
all  presenting,  as  nearly  as  could  be,  about  the  same  area  of 
stimulating  surface  as  the  standard  letters.  The  styles  of 
type  used  were  the  most  varied  that  could  be  found  and  still 
be  legible.  They  were  (i)  a  heavily  shaded  style  of  print, 
(2)  old  English,  (3)  plain  script,  (4)  an  alphabet  of  closed  letters 
similar  to  the  old  English,  but  having  more  flourishes,  and  (5) 
an  alphabet  of  hollow  letters.  All  of  these  were  done  in  black 
by  hand.  Four  series  of  each  kind  of  variation,  size,  color, 
and  style  of  type,  were  given  to  six  subjects  without  varying  the 
spatial  position  of  the  syllables.^  Thus  the  value  of  each  variation 
separately  was  obtained.  Theeffectsof  practice  were  distributed 
by  giving  four  series  each  week,  one  of  each  kind,  and  rotating 
the  time  situation  of  each  kind  each  week.  A  hard  rubber 
mouth  piece  held  between  the  teeth  was  used  to  aid  the  subject 
in  eliminating  enunciation.  It  was  found  as  shown  in  the 
table  below  that  in  immediate  recall  the  series  varying  in  size 
gave  slightly  better  results  than  the  standard — a  gain  of  9  per 
cent,  but  that  color  variation  was  of  no  aid,  while  variation  in 
the  style  of  print  was  a  detriment.  In  recall  after  24  hours, 
however,  the  result  was  quite  different.  was  again  the 

^  The  standard  series  did  not  vary  in  size,  color  or  style  of  type.  They 
were  the  standard  with  which  the  others  were  compared. 

^  For  further  details,  see  p.  25. 


i8 


HARVEY  ANDREW  PETERSON. 


best  variation,  showing  a  gat  71.  over  standard  of  ^8  per  cent. 
Color  was  next  with  J2  per  cent  gain,  while  even  form  variation 
showed  a  gam  of  ig  per  cent.^ 

The  next  step  was  to  increase  the  complexity  by  combining 
the  variations.  In  each  syllable  shown  him  the  subject  faced  a 
new  combination.  The  most  complex  type  were  series  which 
varied  in  four  ways;  size,  color,  form  or  style  of  lettering  and 
spatial  position.  A  second  type  varied  in  two  ways  only,  the 
two  which  in  all  probability  were  the  most  effective  singly, 
namely,  position  and  size.  The  third  type  was  simply  the 
standard  without  variation  in  position.  Four  series  of  each 
were  given  as  before,  and  it  was  found  that  one  had  not  far 
to  go  to  reach  the  limit  of  effectiveness  in  this  direction.  In 
immediate  recall  the  two  variations  showed  a  gain  of  15  per 
cent,  while  the  series  containing  four  was  no  better  than  stand¬ 
ard,  a  gain  of  3  per  cent.  In  recall  after  zp  hours  the  two  varia¬ 
tions  showed  a  gain  over  standard  of  only  p  per  cent,  while  the 
four  gave  the  same  as  standard  again.  The  improvement  shown 
by  the  subjects  in  the  standard,  y6  per  cent  gain  over  the  show¬ 
ing  made  in  the  first  four  weeks,  is  worth  noting.  It  is  due 
to  practice.  The  unexpected  fact  is  that  the  size  variation  with 
the  addition  of  position  variation  has  not  gained  proportion¬ 
ately.  This  is  probably  due  to  a  concealed  loss  consequent 
upon  increasing  the  complexity.  In  any  case  taken  with  the 
fact  that  four  variations  gave  the  same  as  none  (5.21  and  5.21), 
it  shows  that  the  limit  has  been  reached  with  this  material, 
unless  more  effective  variations  can  be  found. 

During  the  fifth  and  sixth  of  the  eight  weeks  spent  on  syl¬ 
lables,  the  combination  of  size  and  position,  and  the  combina¬ 
tion  of  four  variations  were  tried  with  words.  It  was  expected 
that  the  variations  would  be  of  no  positive  value  here  because 
words  contain  so  much  variation  in  themselves,  especially  in 
meaning,  as  compared  with  syllables.  The  result  as  shown  by 
the  table,  based  on  two  series  of  each  kind,  confirmed  the 
expectation.  Interesting  light  is  thrown  by  the  introspections 
of  the  subjects  on  the  cause  of  the  failure.  They  made  mean- 

‘The  six  horizontal  rows  of  figures  in  the  tables  represent  the  six  subjects, 
and  give  the  average  number  of  syllables  or  words  out  of  nine  correctly  recalled. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  1 9 


ing-classifications  such  as  ‘farm  products’  or  ‘machinery,’ 
which  united  not  only  two  or  more  words  in  the  same  series, 
but  even  words  from  different  series.  With  rare  exceptions, 
position  was  the  only  mechanical  aid,  but  even  it  was  not 
needed  in  view  of  the  variety  afforded  by  meaning.  In  sylla¬ 
bles  they  found  variety  in  ways  not  provided  by  the  operator, 
all  of  which  is  on  the  positive  side  of  our  thesis,  but  which 
cannot  be  reduced  to  tables.  At  the  outset  of  the  experiment 
the  subjects  were  asked  to  lend  their  cooperation  in  shifting 
the  emphasis  of  the  attention  to  the  variations  introduced  by 
the  operator,  and  they  did  so.  Nevertheless,  resemblance  to 
words,  despite  their  efforts  to  exclude  it,  was  one  of  the  two 
main  aids  in  recalling  the  syllables,  the  other  being  position. 
The  fact  that  an  error  had  been  made  in  the  case  of  a  certain 


Table  i.  Showing  averages  and  mean  variations. 
A.  NONSENSE  SYLLABLES. 

Immediate  Recall. 


EFFECT  OF  VARIATIONS  TAKEN  SINGLY. 


EFFECT  OF  COMBINING  VARIATIONS. 


Standard. 

Colors. 

Sizes. 

Forms. 

Standard. 

Two  Var. 

Four  Var. 

Av. 

M.  V. 

Av. 

M.  V. 

Av. 

M.  V. 

Av. 

M.  V. 

Av. 

M.  V. 

Av. 

M.  V. 

Av. 

M.V. 

6.25 

1.25 

6.84 

I  .01 

7.92 

.29 

6.67 

.50 

7-34 

I  .00 

8.41 

•29 

7.00 

•50 

6.67 

I.17 

6.75 

.46 

7.42 

1 .04 

4.92 

•79 

6.59 

•79 

8.00 

I  .00 

7-58 

.80 

7-33 

■83 

7-34 

•34 

8.50 

•75 

6.08 

1-54 

6.17 

•83 

6.83 

.96 

6-33 

•83 

525 

1-75 

4.50 

1 .00 

6.00 

.84 

5-42 

•92 

8-33 

.66 

6.66 

1-33 

7 . 16 

1.42 

525 

.29 

5-92 

•77 

6.17 

•59 

6.09 

.90 

6.42 

1 .08 

9.67 

2.00 

7.17 

I.17 

7.08 

1-59 

6.75 

.88 

5-33 

•50 

5-75 

1-75 

5-33 

1 .08 

6.50 

1 .00 

6.00 

I  .00 

6.31 

I  15 

6-35 

•74 

6.89 

.68 

00 

N) 

1 .08 

6.70 

-91 

00 

1 . 10 

6.88 

.96 

Recall  after  Twenty-four  Hours. 


3 

25 

138 

4-25 

1.88 

4 

00 

1 .00 

3 

75 

1-75 

7 

25 

.88 

7-25 

1.25 

7 

25 

1-75 

4 

25 

1. 19 

325 

1-38 

5 

50 

1.25 

4 

50 

1.50 

4 

75 

1.88 

5-75 

1-38 

3 

50 

1.25 

50 

•75 

3-75 

1.25 

3 

75 

•75 

2 

25 

1. 19 

5 

50 

150 

6.25 

1-75 

4 

75 

1.25 

2 

25 

•38 

4.00 

.50 

4 

50 

1.50 

3 

25 

1.25 

2 

50 

1-55 

2.25 

1-38 

3 

00 

2.00 

4 

25 

1.25 

5.00 

1 .00 

6 

25 

1-75 

5 

00 

.50 

5 

00 

1.50 

5.00 

1 .00 

5 

25 

.88 

5 

50 

1.25 

6.00 

1.50 

7 

50 

.50 

5 

00 

1 .00 

6 

25 

1-75 

6.00 

1 .00 

7 

50 

.50 

3 

33 

1.03 

438 

1-25 

5 

25 

1-13 

3 

96 

1 .20 

5 

21 

1. 51 

5-42 

1.30 

5 

21 

1.27 

20 


HARVEY  ANDREW  PETERSON. 


B.  WORDS. 

Immediate  Recall  Recall  after  Forty-eight  Hours . 

Stand.  Two  Var.  Four  Var.  Stand.  Two  Var.  Four  Var. 

7.2  7.00  6.2  2.94  3.40  1.69 

syllable  individualized  the  syllable  and  was  likely  to  fix  it. 
Thus  one  subject  said  paradoxically  that  the  syllables  that  he 
didn’t  get  in  immediate  recall  were  the  ones  he  got  in  the  test 
for  permanence.^  For  a  while  white  type  on  white  cardboard 
individualized  and  fixated  its  syllables  more  than  colors  or 
grays,  simply  because  it  was  difficult  to  see.  A  doubt  as  to 
the  identity  of  a  letter,  after  being  settled,  was  certain  to  fixate 
the  syllable  concerned. 

If  meaning  is  a  kind  of  variety  which  persons  naturally  seek, 
as  the  work  with  nonsense  syllables  and  words  indicated,  it 
should  be  susceptible  to  measurement.  A  series  of  twenty 
adjectives,  and  another  of  twenty  short  sentences  were  given  to 
five  subjects.  The  adjectives  were: 

Pat,  humble,  young,  happy,  broad,  distracted,  violent,  privileged,  sleek, 
reversed,  cautious,  immediate,  ideal,  polite,  cold,  gabled,  serene,  imaginative, 
various,  trifling. 

The  sentences  were: 

Mammoth  Cave  is  a  wonderful  place.  Cats  are  not  very  teachable.  Pie 
gave  a  prodigious  sniff.  The  naval  gunner  is  often  a  noble  fellow.  Chicago 
is  a  windy  city.  Genteel  is  a  word  seldom  used  today.  Damp  weather  is 
bad  for  rheumatism.  The  need  of  protecting  our  industries  is  a  worn  argument. 
The  mistletoe  is  a  parasitic  plant.  Dogs  are  sociable  companions  for  men. 
The  theatre  is  potent  for  good  as  well  as  evil.  Gambling  is  expensive.  The 
steamer  hit  the  dock  a  hard  bump.  This  thread  is  rotten.  Parks  at  public 
expense  are  easily  justifiable.  Granite  is  a  handsome  building  stone.  The 
lake  is  rough.  The  Japanese  are  a  small  race.  Is  abusive  language  ever 
justifiable  The  owner  of  the  horse  gave  a  sarcastic  smile,  and  declined  the 
offer. 

The  subjects  were  allowed  two  minutes  in  which  to  study 
each  of  the  series,  which  were  given  them  in  typewritten  form. 

^  The  series  were  shown  again  between  immediate  recall  and  the  test  for 
permanence  See  IV  below. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  21 


Following  directions  they  did  not  run  together  successive  terms 
into  larger  units,  and  tried  not  to  expand  words  into  phrases 
or  sentences.  They  were  required  to  read  each  list  through  at 
least  once.  In  the  test  for  immediate  recall  and  for  retention 
after  twenty-four  hours  they  were  required  to  give  only  the 
substance  of  the  sentences,  but  the  words  verbatim.  They 
recalled  an  average  of  12.8  words  and  ii.6  sentences  in  imme¬ 
diate  recall,  and  y.6  words  and  y  sentences  after  Hventy-four 
hours.  One  of  the  five  did  worse  in  the  sentences  than  in  the 
words,  the  other  four  did  as  well  in  one  as  in  the  other.  The 
subjects  said  it  was  difficult  to  keep  the  words  from  arousing 
mentally  a  thought-situation  which  expressed  in  language 
would  have  been  one  or  more  sentences.  Yet  it  is  not  to  be 
inferred  that  the  two  lists  became  equivalent.  The  tendency 
existed  in  that  direction,  and  the  attempt  to  inhibit  it  was 
partially  a  failure.  The  difficulty  of  controlling  the  material 
led  to  its  discontinuance.  Perhaps  the  significant  feature,  aside 
from  the  tendency  toward  expansion  mentioned,  is  the  fact 
that  the  sentences  are  remembered  as  zuell  as  the  words. 

Numbers  are  a  material  apparently  difficult  to  read  connected 
thought  into,  especially  when  given  in  extended  series.  They 
.  seem  at  times  not  very  far  from  a  dead  level  of  monotony.  Yet 
they  may  be  vivified  by  associated  material.  Three  series  of 
each  of  the  following  two  kinds  were  given;  on  the  one  hand 
series  of  two-place  numbers,  seven  numbers  in  a  series;  on 
the  other  hand  three  series  of  similar  numbers  and  beside  each 
a  biographical  fact  from  the  Renaissance  period  of  Itnlian 
history.  The  facts  were  varied  and  some  were  striking.  One 
of  the  series  of  numbers  and  facts  was  as  follows; 


Series  III. 

51  A  sculptor. 

93  Famous  for  an  impromptu  oration  in  Latin  congratulating  the  Emperor 
Frederick  III  on  his  coronation. 

14  A  merchant  of  Pisa.  Introduced  the  Arabic  notation  into  European 
commercial  life. 

47  A  monk. 

26  Naples. 


22 


HARVET  ANDREW  PETERSON. 


79  An  instance  of  the  revival  of  oratory.  Funerals,  marriages  and  installa¬ 
tions  of  bishops  were  among  the  occasions  of  his  efforts. 

85  A  bishop. 

It  was  expected  that  the  numbers  without  facts  would  be 
learned  in  less  time  than  those  accompanied  by  facts,  but  it 
was  thought  that  the  latter  might  be  retained  better.  Two 
new  series  were  given  each  week,  one  of  each  kind.  Typewritten 
cards  each  containing  a  series  were  given  the  subject,  one 
at  a  time.  In  the  case  of  the  numbers  without  the  facts  he 
memorized  the  list  as  rapidly  as  possible,  the  time  record  being 
kept  by  the  operator  with  a  stop  watch.  As  soon  as  the  subject 
thought  he  could  give  the  list  correctly  he  tried.  If  he  failed, 
the  learning  process  was  resumed,  and  this  continued  until  he 
gave  the  list  correctly.  The  next  day  the  series  learned  on  the 
previous  day  was  tested,  and  if  an  error  was  made,  that  series 
was  relearned,  and  so  on  until  the  subject  held  the  series  cor¬ 
rectly  for  24  hours.  This  was  the  standard  of  learning  up  to 
which  the  series  were  brought  before  they  were  dropped.  With 
no  subsequent  renewings  they  were  tested  for  permanence  of 
retention  seven  days  and  again  thirteen  days  after  the  comple¬ 
tion  of  learning.  The  series  of  numbers  and  facts  were  learned 
in  the  same  way,  except  that  in  the  tests  the  subject  was  required 
to  give  the  substance  of  the  facts  with  their  appropriate  num¬ 
bers.  We  refer  here  to  the  learning  process. 

The  results  are  given  in  Table  2.  The  first  half  gives  the 
total  learning  times  in  minutes  and  seconds.  3:31  means  3 
mins.  31  secs.  In  the  second  half,  in  which  the  recall  is  given, 
the  figures  indicate  the  number  of  numbers,  or  numbers  and 
facts  which  were  correctly  recalled.  Seven  would  be  a  perfect 
score  for  a  series.  No  credit  was  allowed  for  partially  correct 
numbers,  or  for  numbers  or  facts  apart  from  their  correct 
coupling.  Several  cases  where  the  recall  could  not  be  secured 
are  marked  by  dashes  in  the  table. 

The  numbers  alone  are  learned  in  less  than  one-half  the  time 
taken  by  the  numbers  and  facts,  and  are  retained  quite  a  little 
better. 

This  ended  our  experiments  with  language  materials.  We 
may  summarize  them  as  follows:  Typographical  variations 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  23 


Table  2.  Renaissance  Senes. 


LEARNING  TIMES. 


Subjects. 

NUMBERS. 

NUMBERS  AND  FACTS, 

AVERAGES. 

I. 

II. 

III. 

I. 

II. 

III. 

Nos. 

Nos. and 
Facts. 

McP . 

3 

:  31 

I  :  50 

2 

39 

9  :  15 

7  : 

30 

6  : 

26 

2 

:  40 

7  :  44 

G . 

••  57 

I  :  43 

I 

23 

10  :  15 

8  : 

1 1 

9  : 

37 

I 

;  21 

9  :  21 

H . 

7 

:  17 

I  :  36 

3 

28 

7  :  50 

4  : 

41 

5  : 

25 

4 

:  07 

5  :  59 

J . 

2 

:  40 

3  •  27 

3 

:49 

10  :  28 

10  : 

09 

12  : 

24 

'■> 

:  19 

II  :  00 

L . 

6 

:  18 

5  :  20 

3 

42 

9  :  36 

6  : 

21 

7  : 

06 

5 

:  07 

7  =41 

F . 

4 

:  26 

3  :  51 

3 

23 

8  :  00 

6  : 

35 

5 

05 

3 

:  53 

6  :  33 

Av . 

4 

:  12 

_ ^ 

3 

04 

9  :  H 

7  : 

15 

7  ; 

41 

3 

;  25 

8  :  03 

NUMBER  OF  TERMS  RECALLED. 


AFTER  SEVEN  DAYS. 

AFTER  THIRTEEN  DAYS. 

Numbers. 

Nos.  and  Facts. 

Numbers. 

Nos.  and  Facts. 

I. 

II. 

III. 

I. 

II. 

III. 

I. 

II. 

III. 

I. 

II. 

III. 

McP.  .  . 

7 

4 

7 

7 

I 

6 

5 

0 

7 

3 

I 

5 

G . 

7 

4 

2 

7 

I 

2 

3 

I 

5 

5 

0 

2 

H . 

3 

6 

7 

6 

4 

5 

3 

5 

- 

5 

3 

- 

J . 

I 

2 

0 

2 

4 

7 

0 

0 

- 

0 

4 

— 

L . 

.  I 

4 

7 

3 

I 

4 

I 

2 

7 

2 

I 

4 

F . 

5 

5 

5 

3 

2 

2 

4 

3 

5 

I 

I 

2 

Av . 

4 

4.2 

4-7 

4-7 

2.2 

4-3 

2-7 

1.8 

6 

2.7 

1-7 

2.3 

AVERAGES. 


After  seven  days. . , 
After  thirteen  days 


Numbers  and 
Numbers.  Facts. 

4-3  3-7 

3.2  2.4 


are  at  first  a  strong  aid  in  retaining  nonsense  syllables,  but  in 
the  course  of  two  and  a  half  months  the  advantage  of  series 
varying  in  this  way  is  lost,  because  of  improvement  of  the 
ordinary  series  through  practice.  With  words  the  typograph¬ 
ical  variations  are  of  no  aid  whatever.  The  meaning  variation 


24 


HARVET  ANDREW  PETERSON. 


is  far  more  important  and  is  the  kind  of  variation  relied  on. 
The  results  have  an  interesting  bearing  on  the  theory  of  adver¬ 
tising  and  printing.  Our  own  conclusion  is  that  if  typograph¬ 
ical  variations  have  any  value  here  for  memory  they  must  olher 
a  constant  novelty.  Mere'  variation  without  a  very  consider¬ 
able  amount  of  newness  is  of  no  aid.  If  there  is  to  be  simply 
change  from  one  familiar  variation  (or  even  new  combination 
of  familiar  variations)  to  another,  then  the  variation  in  the 
sense  is  the  more  attractive  and  influential,  in  fact  the  only 
thing  that  is  influential.  This  may  tax  the  printer  rather 
severely,  but  it  is  some  encouragement  to  those  who  depend 
on  the  content  of  their  advertisements,  rather  than  on  the  form. 

When  mechanical  variations  are  left  and  the  attempt  is  made 
to  secure  variety  through  meaning,  the  first  part  of  our  results 
are  positive,  the  second  part  indecisive.  Sentences  are  as  well 
remembered  as  words,  when  the  learning  time  is  long  enough 
to  comprehend  both.  Binet  and  Henri  and  others  had  already 
shown  this,  but  our  lists  of  words  and  corresponding  sentences 
were  much  longer  than  theirs.  A  still  further  increase  in  the 
length  of  the  selections  would  without  doubt  show  the  same 
result.  The  negative  results  of  our  experiments  with  numbers 
and  biographical  facts  are  to  be  interpreted  as  a  superiority  of 
preformed  associations  over  associations  required  to  be  formed 
during  the  learning  process.  In  the  series  of  numbers  without 
facts  the  subjects  could  not  prevent  the  numbers  from  suggest¬ 
ing  associations  from  their  past  experiences.  57  became  57th 
St.,  65  the  age  of  a  member  of  the  family,  etc.  Dates,  too, 
were  suggested  by  some  of  the  numbers.  The  impossibility  of 
controlling  the  associations  led  to  the  discontinuance  of  the  use 
of  numbers.  A  similar  difficulty  has  been  mentioned  already 
in  connection  with  the  use  of  lists  of  words. 

In  the  next  section  we  propose  to  make  a  brief  digression  to 
discuss  a  question  of  nonsense  syllable  technique.  It  may  be 
omitted  without  detriment  to  the  comprehension  of  the  main 
problems  under  consideration. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY .  25 


IV.  ON  METHODS  OF  LEARNING  AND  TESTING  NONSENSE 

SYLLABLES. 

The  method  of  learning  the  series  of  nonsense  syllables  in 
III  consisted  in  giving  the  various  series  to  be  compared  equal 
numbers  of  repetitions,  extending  the  learning  process  over  two 
days,  and  securing  an  immediate  recall  on  the  first  day  and  a 
recall  after  24  hours  on  the  third  day.  On  the  first  day  the 
subject  was  given  2  repetitions  of  a  series  in  practically  imme¬ 
diate  succession  and  then  tested  for  immediate  recall,  the  test 
being  the  quantity  of  syllables  recalled  and  the  cue,  simply  the 
direction  to  begin.  This  was  followed  by  5  repetitions.  The 
next  day  the  subject  spent  from  5  to  10  minutes,  the  exact 
amount  determined  by  the  operator  and  depending  on  the 
number  of  series,  in  recalling,  as  before,  as  many  syllables  as 
he  could.  Placing  in  the  proper  series  was  understood  to  be 
not  essential.  This  was  followed  by  3  repetitions.  On  the 
third  day  without  further  seeing  the  series  and  with  no  other 
cue  than  an  enumeration  by  the  operator  of  the  varieties  of 
series  which  had  been  given,  the  subject  again  wrote  as  many 
syllables  as  he  could  recall.  There  was  no  time  limit  on  this 
test.  The  intervals  between  repetitions  and  series  were  prop¬ 
erly  regulated,  and  kept  constant.  Reviewing  was  permitted 
during  the  progress  of  a  repetition  but  not  between  repetitions. 
The  rate  was  50  beats  of  the  metronome  per  minute  with  an 
exposure  on  every  alternate  beat.  The  large  percentages  of 
recall  in  the  tables  speak  in  favor  of  the  workableness  of  the 
method. 

The  method  has  advantages  over  several  of  those  currently 
in  use.  In  the  Ebbinghaus  method  of  entire  learning  and  re¬ 
learning,  if  the  series  are  short,  for  example  nine  syllables,  the 
repetition  is  too  gross  a  measure  to  detect  small  differences. 
The  difference  of  i  repetition  between  the  4  and  the  5  (let  us 
say)  necessary  for  perfect  immediate  recall  of  two  nine-syllable 
series  may  represent  the  recovery  of  a  single  consonant,  or 
18  seconds  of  hard  work  on  the  part  of  the  subject.  Our 
method  gets  over  this  difficulty  by  giving  a  fixed  number  of 
repetitions,  the  same  for  the  various  types  to  be  compared  and 


26 


HARVET  ANDREW  PETERSON. 


measures  the  difference  by  the  percentages  of  recall.  The 
method  of  successes,  used  by  Muller  and  Pilzecker  and  many 
others,  also  has  this  advantage,  but  has  one  objection  that  in 
our  opinion  is  fatal  to  it  for  many  subjects,  in  fact  most  sub¬ 
jects.  It  encourages  word  associations.  The  two  syllables 
constituting  a  couplet  are  likely  to  suggest  to  a  subject  single 
words  or  phrases  which  form  a  unity  in  his  past  experience  and 
serve  here  to  link  the  two  syllables  together.  Gan  muc  sug¬ 
gests  gander  mud,  laj  gul  suggests  large  girl.  The  difficulty 
is  a  well-known  one  and  is  treated  by  Ebbinghaus  in  his  Grund- 
ziige,  p.  676.  It  is  present  to  some  extent  in  the  non-couplet 
methods,  but  the  couplet  methods  (Treffermethoden)  greatly 
increase  the  frequency  of  occurrence.  In  an  investigation 
made  some  years  ago  it  was  demonstrated  that  couplets  in 
which  word  associations  of  this  sort  occurred  were  better 
retained  than  the  rest  of  the  series,  and  the  superiority  was 
measured.^  Under  certain  conditions,  which  do  not  concern  us 
here  since  they  were  the  same  for  both  kinds  of  material, 
couplets  in  which  word  associations  did  not  occur  had  a  recall 
of  63  per  cent  correct  after  one  day,  which  sank  to  19  percent 
after  fifteen  days  more.  In  contrast  with  this,  couplets  in  which 
word  associations  occurred  had  a  recall  of  82  per  cent  correct 
after  one  day,  which  sank  only  to  64  per  cent  after  fifteen  days 
more.  The  results  were  based  on  six  subjects  and  64  couplets 
altogether,  of  which  somewhat  the  larger  share  were  couplets 
in  which  no  word  associations  occurred.  If  the  couplets  in 
which  word  associations  occurred  were  thrown  out  or  separated, 
there  would  be  no  objection  to  this  method,  but  the  waste  of 
effort  is  great,  and  it  has  never  been  done  to  the  writer’s  knowl¬ 
edge,  except  in  the  investigation  just  quoted. 

Our  method  makes  an  economical  use  of  the  experimenter’s 
and  the  subject’s  time  by  using  short  series  and  distributing  the 
learning  over  two  days.  By  making  the  amount  recalled, 
instead  of  the  number  of  repetitions  required  to  learn,  the 
means  of  measurement,  it  measures  small  differences.  It  keeps 
the  word  association  factor  at  a  minimum.  If  it  has  an  objec- 

‘  Peterson,  H.  A.  Recall  of  Words,  Objects  and  Movements.  Psych.  Rev., 
1903,  Mon.  Sup.,  iv,  p.  232. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  27 


tion,  it  is  the  possibility  that  the  recall  after  the  last  twenty- 
four  hours  may  not  be  enough  for  purposes  of  comparison. 
This  is  doubtless  true  of  some  subjects.  In  the  foregoing  experi¬ 
ments,  P  was  such  a  subject.  This  objection  would  not  hold 
for  the  five  other  subjects  employed  by  us,  with  all  of  whom 
the  recall  was  sufficient  for  comparison. 

V.  EXPERIMENTS  WITH  PLANE  AREAS 

I.  Adding  Variations  to  a  Material  Containing  Little 

Variation 

The  next  material  selected  was  both  simple  and  highly  sim¬ 
ilar  internally.  Different  shades  of  gray  were  associated  with 
their  spatial  positions  on  a  cardboard  area.  Four  series  were 
given,  the  first  of  which  varied  in  shades  of  gray  only,  the 
second  in  gray  and  the  color  of  the  center,  the  third  in  gray 
and  the  size  of  the  different  presentations  of  the  series,  and  the 
fourth  in  gray  and  the  shape  of  the  presentations.  The  same 
seven  grays  were  used  in  all  four  series.  They  were  the  Her- 
ing  papers  Nos.  i,  2,  5,  8,  19,  35  and  49.  Each  series  had  seven 
terms  or  presentations  in  it,  and  the  shades  of  gray  ranged 
from  black  to  white  with  about  equal  differences  between 
nearest  shades.  All  seven  terms  were  exposed  simultaneously. 
The  gray  sizes  may  be  given  as  a  sample  series.  They  were, 
from  left  to  right  as  follows: 

Oblongs,  height  twice  the  width.  Dark  gray  128  sq.  cm.;  very  light  gray, 
40.5  sq.  cm.;  white,  60.5  sq.  cm.;  black,  2  sq.  cm.;  medium  gray,  84.5  sq.  cm.; 
light  gray,  8  sq.  cm.;  very  dark  gray,  24.5  sq.  cm. 

The  form-varying  series  is  shown  in  the  plates  in  the  Appen¬ 
dix.^  All  of  the  series  except  the  one  which  varied  in  size  were 
composed  of  terms  whose  areas  were  50  sq.  cm.,  and  even  the 
size  series  had  the  same  total  area  as  the  other  three,  viz:  350 
sq.  cm.  The  color-varying  series  were  made  by  pasting  small 
oblongs  of  color  1.5  cm.  wide  and  3  cm.  high  on  the  gray 
oblongs,  themselves  5  cm.  wide  and  10  cm.  high.  Each  of  the 
series  was  mounted  on  a  sheet  of  white  cardboard  22  X  28 
inches,  with  the  longer  side  as  the  base. 

^  Gray  Forms. 


28 


HARVET  ANDREW  PETERSON. 


Conceivably  the  ease  of  memorizing  such  series  would  depend 
greatly  on  the  order  of  succession  of  the  terms.  However, 
inasmuch  as  one  of  the  purposes  of  the  investigation  was  to 
obtain  information  on  this  point,  aside  from  certain  obviously 
easy  arrangements,  it  was  thought  best  to  determine  it  by 
chance.  The  following  cases  embrace  all  exclusions:  (i)  in 
sizes,  a  continuous  increase  followed  by  a  continuous  decrease, 
or  vice  versa;  or  a  continouus  increase  alone  or  decrease  alone; 
(2)  in  shades  of  gray,  or  violet  (the  latter  series  to  be  described 
later)  a  continuous  change  from  black  to  white  or  vice  versa, 
or  from  red  to  purple  or  vice  versa;  (3)  in  grays,  colors,  and 
sizes,  the  same  arrangement  as  some  previous  series.  This 
rule  resulted  probably  in  less  uniformity  of  material,  but  at  least 
was  free  from  the  influence  of  unconscious  subjective  favoring. 

To  increase  the  number  of  series  a  group  of  four  series  was 
next  made  which  in  all  respects  was  similar  to  the  gray  group 
except  that  shades  and  tints  of  violet  were  used.  The  colors 
in  the  series  with  colored  centers,  and  the  shapes  in  the  form- 
varying  series  were  different  from  what  had  been  used  in  the 
gray  group.  The  shapes  are  given  in  the  plates.  The  same 
sizes  were  used  in  the  size-varying  series  as  in  the  grays,  but 
to  diminish  interference  from  the  gray  sizes  they  were  right 
triangles.  The  effort  was  made  to  secure  violets  which  would 
be  about  as  difficult  to  discriminate  as  the  grays.  The  ones 
selected  were:  blue  violet,  violet,  violet  tint  i,  red  violet,  red 
violet  tint  i,  violet  red.  To  these  purple  was  added.  The 
grays  were  learned  the  first  week  and  the  violets  the  second  week. 

The  method  of  learning  the  series  was  the  same  as  the  one 
used  in  experiments  with  numbers  and  biographical  facts.  We 
shall  describe  the  process  in  its  several  steps.  When  the  shutter 
opened  the  subject  began  to  learn  the  series.  As  soon  as  he 
thought  he  had  mastered  it,  so  that  he  could  give  it  the  next 
day,  he  gave  a  signal,  whereupon  the  shutter  closed.  The 
subject  then  turned  to  a  small  table  on  his  right,  uncovered  a 
set  of  unmounted  duplicates  of  the  series,  and  tried  to  arrange 
them  in  the  right  order.  As  soon  as  he  had  arranged  the 
series  as  best  he  could  he  gave  a  signal,  whereupon  the  operator 
at  once  removed  the  duplicates.  If  the  attempt  was  unsuc- 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  29 

cessful,  the  duplicates  were  returned  bunched  and  covered,  the 
series  was  again  exposed  and  the  learning  process  resumed,  and 
again  tested,  till  the  series  had  been  perfectly  arranged.  The 
lengths  of  exposure  were  kept  with  a  stop-watch. 

Where  more  than  one  exposure  of  the  series  a  day  was  neces¬ 
sary,  the  lengths  of  the  exposures  were  recorded  separately, 
and  the  number  of  arrangements  which  the  subject  required. 
The  next  day  the  series  given  on  the  previous  day  were  tested 
again  by  use  of  the  duplicates.  If  the  arrangement  of  any 
series  contained  an  error,  that  series  was  again  exposed  for 
such  a  length  of  time  as  the  subject  required,  and  again  tested. 
The  subject  could  not  omit  the  arranging  if  he  desired.  If  he 
showed  by  his  preliminary  arrangement  on  the  second  day  that 
he  had  held  the  series  perfectly  for  a  day,  it  was  not  again  shown. 
Having  been  brought  up  to  the  standard,  the  series  was  dropped 
for  thirteen  days,  when  the  retention  test  took  place.  The 
learning  was  usually  completed  by  the  third  day.  The  pur¬ 
pose  of  all  this  was  to  bring  the  series  up  to  a  point  of  imme¬ 
diate  fixation  that  would  insure  enough  recall  after  two  weeks 
for  purposes  of  comparing  the  different  types  of  series.  The 
test  which  was  given  after  thirteen  days  consisted  in  the  sub¬ 
ject’s  again  arranging  the  series.  No  introspections  were 
allowed  and  no  comments  could  be  given  till  after  this  test, 
because  such  introspections  or  comments  would  fixate  the 
series,  and  do  it  unevenly.  For  introspections  our  main  reliance 
was  on  series  given  especially  for  this  purpose  and  not  recorded 
in  the  tables.  Reviewing  after  an  arrangement  had  been  made 
was  not  allowed.  Having  arranged  the  duplicates  the  subject 
who  followed  instructions  dismissed  the  series  from  his  mind. 
The  intervals  between  exposures  and  between  series  were  regu¬ 
lated. 

Toward  the  end  of  the  investigation  a  series  of  experiments 
was  carried  out  upon  the  same  subjects  with  similar  material 
for  the  purpose  of  determining  the  value  of  the  practice  of 
allowing  the  subject  to  arrange.  The  details  are  given  on  pp. 
65-7,  which  may  be  profitably  read  at  this  point.  The  method 
employed  consisted  in  giving  parallel  series  as  nearly  equal  in 
difficulty  as  possible.  In  one-half  of  them  the  learning  was 


3° 


HARVET  ANDREW  PETERSON. 


carried  on  solely  by  looking  at  the  series  through  the  aperture. 
The  other  half  were  given  the  same  lengths  of  exposure  and  in 
addition  the  subject  was  allowed  the  usual  arrangement  of 
duplicates.  The  recall  after  the  lapse  of  a  week  gave  the  rela¬ 
tive  efficiency  of  the  two  methods  of  learning,  and  by  sub¬ 
tracting  the  total  recall  of  all  the  series  in  which  there  was  no 
arranging  from  the  total  recall  of  the  series  in  which  arranging 
had  been  allowed,  the  value  of  the  arrangements  alone  was 
obtained.  Since  a  given  number  of  arrangements  produced  a 
certain  number  of  units  of  recall  and  a  given  amount  of  time 
of  exposure  produced  a  certain  number  of  units  of  recall,  by 
reducing  both  to  the  amounts  of  each  necessary  to  produce  one 
unit  of  recall  it  was  possible  to  find  for  an  arrangement  its 
equivalent  in  minutes  and  seconds  of  learning  time.  With  this 
average  value,  one  for  each  subject,  the  arrangements  were 
converted  into  learning  time  and  added  to  the  amounts  actually 
consumed  by  a  subject  in  looking  at  the  series  through  the 
aperture.  Thus  our  two  time  measurements  were  reduced  to 
one. 

This  in  brief  was  our  method.  In  one  way  it  lacked  exact¬ 
ness,  namely,  in  the  distribution  of  the  learning  periods  over 
varying  numbers  of  days.  But  in  another  way  it  had  exactness. 
By  making  the  subject  the  judge  of  the  time  necessary  for 
learning,  learning  times  were  secured  which  minute  for  minute 
represented  equivalent  degrees  of  effort.  A  comparison  of  the 
subjects’  speed  of  learning  given  on  page  64  will  convince  any 
one  of  the  impossibility  of  getting  accurate  results  when  giving 
the  same  exposure  intervals  to  all  subjects  and  for  all  materials. 
The  difficulty  of  appraising  the  value  of  the  tests  allowed  the 
subjects  during  learning — a  difficulty  which  has  been  felt  by 
many  experimenters  on  memory — ^was  satisfactorily  solved  by 
the  method  described.  Again,  one  of  the  principal  advantages 
of  our  method  is  the  opportunity  it  affords  for  studying  different 
types  of  learners.  The  fact  that  one  series  was  learned  more 
thoroughly  than  another,  that  the  subject  could  not  judge 
accurately  his  ability  to  hold  a  series  for  a  day,  did  not  introduce 
error  into  the  results  if  the  assumption  be  granted  that  recall 
after  thirteen  days  is  in  proportion  to  the  thoroughness  of  the 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  3 1 

original  mastery.  Any  one  who  doubts  this  can  find  evidence 
in  our  tables  in  the  form  of  mean  variations. 

The  use  of  duplicates  as  a  means  of  testing  was  adopted  to 
avoid  as  far  as  possible  the  inequalities  which  would  be  intro¬ 
duced  into  the  material  by  the  ready  presence  or  absence  of 
names.  Lehmann^  and  Angell,^  among  others,  have  shown 
that  colors  which  can  be  readily  named  are  better  discrimi¬ 
nated  and  remembered  than  those  which  cannot  be.  Again, 
the  desire  of  the  author  was  to  guide  the  whole  investigation 
away  from  language  and  into  retention  and  learning  of  the 
material  presented.  The  initials  of  the  colors  could  be  made 
into  a  mnemonic  word  and  thus  remembered,  and  similarly 
sizes  and  forms.  There  was  no  desire  to  experiment  in  the 
linguistic  field  here,  and  the  subjects  were  repeatedly  turned 
in  the  opposite  direction  and,  judging  by  their  own  testimony, 
with  success.  The  part  played  by  language  is  discussed  on 
p.  47  in  connection  with  methods  of  learning. 

The  results  of  the  gray  and  violet  sets  are  given  in  Table  3. 
The  learning  times  are  given  in  minutes  and  seconds  and 
arrangements;  for  instance,  F.  learned  the  grays  in  4  mins. 
I  sec.  and  2  arrangements.  The  abbreviation  ‘arrs.’  means 
number  of  arrangements  which  the  subject  required  in  bringing 
the  series  up  to  standard.  The  recall  in  the  second  half  of  the 
table  is  based  on  a  method  of  scoring  which  briefly  was  this. 
Perfect  score  for  a  series:  14.  Each  term  allowed  i  for  correct 
absolute  position  (left  end,  or  second  from  there,  etc.)  and  i 
for  correct  relative  position  (having  the  correct  terms  on  both 
sides  of  it).  One-half  for  next-to-correct  absolute  position, 
e.  g.,  4th  or  6th  from  left  end  instead  of  5th.  One-half  for 
one  neighbor  correct,  and  one-quarter  for  each  neighbor  cor¬ 
rect  but  on  the  wrong  side.  Terms  whose  relative  positions 
are  made  incorrect  by  the  errors  of  the  other  terms  lose  no 
credit  themselves. 

The  table  shows  that  when  the  shades  of  gray  and  violet  are 
varied  in  form  and  size,  or  when  they  are  given  colored  centers, 
there  is  a  marked  reduction  in  the  learning  times  and  a  large 

^  Phil.  Studien,  V,  1889,  p.  96. 

*  Phil.  Studien,  XIX,  1902,  p.  1 


32 


HARVEY  ANDREW  PETERSON. 


Table  3.  Areas  varied  tn  Color,  Size  and  Form. 
A.  Learning  Times. 


SUBJECTS. 

GRAYS. 

G.  FORMS. 

G.  SIZES. 

COL.  GRAYS. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

F . 

4 

01 

2 

2 

:  42 

2 

3 

:  22 

2 

3 

30 

2 

Me  P. . 

5 

10 

7 

:  54 

2 

I 

:  02 

5 

2 

01 

4 

G . 

I 

:48 

8 

:  30 

3 

:  52 

7 

46 

2 

H . 

I 

51 

2 

••  43 

2 

I 

=  38 

4 

2 

15 

2 

J . 

4 

24 

3 

I 

:  12 

2 

I 

:  47 

2 

2 

20 

2 

L . 

3 

34 

5 

I 

:  25 

2 

I 

:  37 

4 

2 

21 

4 

Av . 

3 

28 

4-5 

I 

:  14 

2.17 

I 

:  43 

4 

2 

12 

2.67 

VIOLETS. 

V.  FORMS. 

V.  SIZES. 

C.  VIOLETS. 

F . 

4 

:  34 

3 

55 

2 

I 

:  42 

2 

I  :  30 

2 

Mc.P . 

8 

:  00 

10 

43 

2 

I 

••  47 

6 

I  :  46 

4 

G . 

I 

:  45 

7 

54 

2 

I 

:  19 

4 

I  :  23 

4 

H . 

2 

:  51 

6 

35 

2 

I 

:  09 

2 

I  :  05 

2 

J . 

4 

:  41 

4 

39 

4 

I 

:  13 

2 

I  :  50 

2 

:47 

2 

29 

4 

I 

••  25 

4 

2  :  22 

6 

Av . 

3 

:  46 

5-33 

:  43 

2.67 

I 

:  26 

3-33 

I  :  39 

3-33 

B.  Recall  after  Thirteen  Days. 


GRAYS. 

VIOLETS. 

G.  FORMS. 

V.  FORMS. 

G.  SIZES. 

V.  SIZES. 

COL. 

GRAYS. 

COL. 

VIOLETS. 

F . 

6.50 

4.00 

6.00 

14.00 

4.00 

5.00 

11.50 

14.00 

Mc.P . 

4.00 

6.00 

8.75 

6.00 

14.00 

6.50 

8.50 

9.00 

G . 

9-50 

6.00 

4.00 

14.00 

6.25 

6.00 

4.00 

4.00 

H . 

4.00 

6.50 

9.00 

11.50 

4.00 

7-25 

10.00 

10.50 

J . 

5.00 

4.00 

7.00 

14.00 

4.00 

8.25 

4.00 

4.00 

L . 

4.00 

9.00 

11.50 

14.00 

4.00 

4.00 

6.50 

4-75 

Av . 

5.50 

5.92 

7.71 

12.25 

6.04 

6.17 

7.42 

7-71 

increase  in  recall.  If  the  arrangements  be  converted  into  learn¬ 
ing  times,  and  an  average  be  taken  of  the  gray  and  violet  sets 
together,  the  addition  of  a  form  variation  reduces  the  learning 
time  68  per  cent  and  increases  the  recall  yy  per  cent.  The  addi- 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  33 

tion  of  a  variation  in  size  reduces  the  learning  time  about  jO  per 
cent  and  increases  the  recall  J  per  cent.  The  addition  of  a 
variation  in  color  reduces  the  learning  time  /f.^  per  cent  and 
increases  the  recall  per  cent.  Form  is  therefore  the  most 
effective  variation,  color  next  and  size  the  least.  All  six  sub¬ 
jects  benefit  by  all  three  variations.  The  improvement  is 
extremely  marked  and  very  general. 

The  question  arises  whether  the  variations  in  color,  form 
and  size  were  not  easier  to  associate  with  position  than  the 
grays  and  violets,  and  were  therefore  taken  as  the  thing  to  be 
learned,  the  grays  and  violets  being  neglected.  In  other  words, 
was  the  improvement  due  to  substitution  rather  than  to 
increasing  complexity  ^  Did  the  subjects  use  the  shades  of 
gray  and  the  violet  colors  at  all  The  likelihood  that  this  did 
occur  is  increased  by  the  fact  that  interference  was  likely  to 
enter  from  the  connection  of  the  same  shades  of  gray  with 
different  positions  in  different  series,  and  the  same  for  violets. 
The  opinion  of  the  subjects  on  this  point  is  of  value.  They 
said  that  the  grays  (or  violets)  and  their  added  variations 
formed  unities  before  the  learning  process  was  comipleted,  but 
that  the  variations  added  to  the  grays  or  violets,  being  the  more 
easily  discriminated,  were  the  main  reliance  in  learning  and 
recalling. 

The  experiment  does  not  tell  us  whether  the  combination  of 
two  variations,  in  themselves  about  equal  in  discriminability, 
would  be  more  readily  associated  and  better  retained  than  either 
alone.  For  example,  the  table  shows  that  shades  of  gray  and 
violet  colors  without  additional  variations  were  about  equal. 
Would  their  combination  result  in  a  learning  time  and  retention 
better  than  either  alone  ?  While  the  experiment  was  not  per¬ 
formed,  there  is  no  doubt  that  at  this  low  level  of  variation  it 
would. 

To  summarize  the  present  situation  in  the  solution  of  our 
problem:  in  the  shades  of  gray  or  shades  and  tints  of  one  color, 
a  material  has  been  found  which  has  a  rather  large  amount  of 
sameness  and  simplicity  about  it,  and  still  is  free  from  the 
preformed  associations  which  hindered  the  linguistic  experi¬ 
ments.  So  far  as  this  material  is  concerned  the  experiments 


34 


HARVEr  ANDREW  PETERSON. 


just  completed  answer  the  first  part  of  our  thesis.  Adding 
variations  improves  both  the  learning  times  and  retention  of  all 
the  subjects  by  large  amounts,  the  precise  amount  differing  with 
different  variations.  The  next  step  is  to  try  adding  variations 
to  materials  similar  in  their  general  character  to  grays  and 
violets,  but  containing  in  themselves  more  variety  and  com¬ 
plexity. 

2.  Adding  Variations  to  More  Varied  Materials. 

In  this  set  of  experiments  there  was  not  only  an  ascent  to 
more  varied  bases  than  grays  and  violets,  but  there  was  also 
an  effort  to  add  variations  that  were  equal  or  less  in  discrimi- 
nability  than  the  bases  to  which  they  were  added.  Color,  form 
and  size  were  suspected  of  fulfilling  these  conditions.  Twenty- 
four  series  of  six  different  kinds  were  made. 

i  4  series  of  colors  iv  4  series  of  colored  sizes 

ii  4  series  of  sizes  v  4  series  of  colored  forms 

iii  4  series  of  forms  vi  4  series  of  colored  forms  of 

different  sizes.^ 

The  twelve  series  on  the  left  aim  to  find  the  value  of  color, 
size  and  form  separately;  the  twelve  on  the  right,  their  value  in 
combination.  Together  they  should  answer  such  questions  as 
the  following;  Suppose  it  should  result  that  colors  and  sizes 
each  by  themselves  are  learned  about  equally  well.  Are  series 
which  vary  in  both  ways  simultaneously  (colored  sizes)  learned 
more  quickly,  and  retained  better,  or  not }  If  better,  it  can  be 
due  only  to  the  increase  in  complexity  and  resulting  differ¬ 
entiation,  and  not  to  substitution.  In  the  same  way  the  last 
two  groups  on  the  right  may  be  compared  with  the  last  on  the 
left. 

The  general  plan  of  these  series  differed  from  that  of  the 
series  of  grays  and  violets  in  one  important  respect.  The  col¬ 
ored  sizes,  for  example,  did  not  add  a  size  variation  to  the  colors 
of  the  previous  color  series,  but,  as  far  as  the  realm  of  colors 

‘  It  will  be  found  helpful  in  the  comprehension  of  the  following  general 
description  to  read  for  illustrative  purposes  the  construction  of  a  few  typical 
series  in  the  Appendix,  pp.  74-80.  The  Bradley  papers  were  used. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  35 

offered  variety,  combined  size  with  colors  not  heretofore  used. 
Similarly  when  in  the  third,  fifth  and  sixth  groups  of  series 
above  enumerated,  form  became  a  base,  the  same  forms  were 
not  used  over  again,  as  was  the  case  with  the  shades  of  gray 
and  violet,  but  new  forms  were  found.  This  change  was  in 
the  interest  of  a  reduction  of  interference.  The  principle  could 
be  carried  out  most  fully  in  the  case  of  forms,  less  completely  with 
colors,  and  still  less  with  sizes.  Our  guiding  idea  was  to  use 
all  the  wealth  of  variety  which  each  realm,  color,  size  and 
form  afforded.  Our  attitude  was  therefore  an  entirely  prac¬ 
tical  one.  Of  the  76  different  colors  used  in  this  set  and  in  the 
gray  and  violet  sets,  38  were  used  only  once,  18  twice,  14  three 
times  and  6  four  times.  Of  course  the  subjects  did  not  dis¬ 
criminate  in  memory  nearly  as  many  colors.  Of  the  78  differ¬ 
ent  shapes  used  in  the  investigation  with  these  subjects,  48 
were  used  only  once,  26  twice  and  4  three  times.  The  repe¬ 
tition  of  forms  was  confined  entirely  to  two  series  in  each  of  the 
form-varying  groups,  namely.  Forms  I  and  II,  Colored  Forms 
II  and  III,  Colored  Forms  of  different  Sizes  III  and  IV, 
and  these  six  series  were  composed  wholly  of  forms  which  had 
been  used  once  before.  Thus  there  was  a  restricted  area 
within  which  the  effect  of  repeating  forms  could  be  observed. 
It  is  essential  to  note  that  in  respect  to  this  feature  the  three 
form-varying  groups  were  on  an  equal  footing,  for  otherwise 
they  could  not  be  compared.  Wherever  a  form  was  used 
again,  it  was  altered  markedly  in  size  and  color.  With  series 
of  sizes  the  limitations  of  the  apparatus  and  work-room  made 
the  variety  small.  In  certain  extra  series  not  included  in  the 
results  we  tried  the  effect  of  larger  sizes,  but  in  the  size  series 
given  in  the  tables  the  aggregate  area  of  the  seven  terms  of  a 
series  was  in  every  case  350  sq.  cm.,  which  was  the  same  as 
for  all  the  other  series.  Now  within  this  limit  the  numberof 
sizes  which  are  favorable  for  inter-term  discrimination  is  rela¬ 
tively  very  small.  We  found  the  best  showing  for  sizes  could 
be  made  by  restricting  the  choice  to  about  twelve  sizes,  which 
we  did.  The  other  devices  used  for  reducing  interference  were 
to  give  each  series  which  did  not  vary  in  form  or  color  a  dis¬ 
tinctive  color  and  form  of  its  own;  similarly  each  series  of 


36 


HARVET  ANDREW  PETERSON. 


colors  had  a  distinctive  series-form,  etc.  The  series  were 
mounted  on  white  cardboard,  14  X  28  inches,  all  the  terms 
resting  on  a  horizontal  base  line.  A  full  description  of  all  the 
series  used,  including  some  extra  ones  not  reported  in  the 
tables,  but  used  in  the  analysis  of  errors  to  follow  later,  will 
be  found  on  pp.  74-80.  A  few  further  remarks  here  will  give 
a  sufficient  account  of  the  series  for  most  purposes. 

As  it  was  the  intention  to  compare  the  results  of  pure  sizes 
and  colored  sizes  it  was  necessary  to  keep  them  equally  dis- 
criminable  in  size.  This  was  done  by  using  the  same  sizes 
(though  not  in  the  same  shapes)  in  both.  Thus  two  series  of 
pure  sizes  and  two  of  colored  sizes  increased  in  area  in  the 
geometrical  ratio  of  2.77  beginning  with  a  minimum  area  of 
.5  sq.  cm.  The  other  two  series  of  sizes  varied  by  irregular 
ratios  which  decreased  somewhat  toward  the  largest  terms,  but 
they  were  repeated  in  the  other  two  series  of  colored  sizes. 
The  order  in  which  the  terms  of  the  series  were  arranged  was 
determined  by  chance,  excluding  the  exceptions  made  on  p. 
28.  The  twelve  series  varying  in  form  are  reproduced  in  the 
plates  on  a  reduced  scale  and  need  little  further  description. 
All  of  the  forms  in  the  third  and  fifth  types  were  of  the  same 
area,  50  sq.  cm.  The  guiding  ideas  in  the  selection  of  forms 
were  to  keep  within  the  three  classes :  conventional  geometrical 
figures,  very  simple  decorative  designs,  and  relatively  meaning¬ 
less  forms.  The  word  relatively  is  emphasized,  for  those 
subjects  who  looked  for  meaning  in  forms  usually  found  it, — 
meaning  of  some  sort.  The  forms  vary  from  simple  to  some¬ 
what  complex,  but  there  are  no  intricate  forms.  Considerable 
care  was  taken  to  make  the  series  as  nearly  equal  in  difficulty 
as  possible,  with  what  success  will  appear  in  the  sequel. 

These  twenty-four  series  W'ere  given  in  the  same  way  as  the 
gray  and  violet  sets.  The  subjects  worked  on  three,  and  if 
necessary  to  learn  the  series  four,  successive  days  each  W’eek; 
on  one  or  two  occasions,  five  days.  To  distribute  tne  effects 
of  practice  and  interference,  tne  six  types  were  learned  con¬ 
currently,  although  the  Roman  numerals  I,  II,  III  and  IV  do 
not  indicate  the  order  in  which  the  series  were  learned.  All 
the  conditions  not  specifically  mentioned  were  the  same  as  in 
the  gray  and  violet  sets. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  37 


Table  4.  Areas  varied  in  Color,  Size  and  Form.  Associated  with 

Spatial  Position. 

A.  LEARNING  TIMES. 


Colors. 


I. 

II. 

III. 

IV. 

AVERAGES. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

G . 

••53 

4 

39 

2 

=35 

5 

.•30 

4 

^39 

3-75 

H . 

••55 

4 

44 

2 

Ti 

2 

4 

.•48 

3.00 

J . 

1:47 

4 

I 

04 

2 

2:21 

5 

••43 

2 

1 :29 

325 

L . 

I  :oi 

I 

41 

4 

1:25 

5 

1 :02 

3 

1 :02 

325 

N . 

4 

44 

3 

4 

:24 

2 

:30 

325 

R . 

:24 

2 

36 

2 

^38 

5 

:i9 

4 

:29 

3-25 

Av . 

=56 

3-17 

^45 

2.50 

••59 

4-33 

=38 

317 

:5o 

3-29 

Sizes. 


G . 

36 

6 

:33 

2 

36 

4 

41 

5 

37 

4.25 

H . 

26 

2 

:20 

2 

46 

6 

=33 

4 

31 

3  50 

J . 

35 

2 

1 :40 

4 

I 

31 

4 

1 :02 

4 

I 

12 

3-50 

L . 

50 

2 

••39 

2 

47 

4 

^43 

4 

45 

3.00 

N . 

34 

8 

:i4 

4 

49 

6 

I  :o4 

8 

40 

6.50 

R . 

14 

2 

:22 

4 

31 

4 

:29 

4 

24 

3-50 

Av . 

•33 

3-67 

••38 

3 

=50 

4.67 

T5 

483 

••42 

4.04 

Forms. 


G . 

H . 

J . 

L . 

N . 

R . 

:26 

:38 

^31 

=39 

T5 

:24 

2 

2 

4 

2 

3 

4 

:4i 

^50 

=35 

:40 

:2i 

;i8 

2 

2 . 

2 

2 

2 

4 

:2i 

:30 

:27 

^31 

:i2 

:i3 

2 

2 

2 

2 

2 

3 

:27 

:23 

••38 

Ti 

:io 

:i8 

2 

2 

2 

2 

2 

2 

:29 

■35 

:34 

•38 

:22 

;i8 

2.00 

2.00 

2.50 

2.00 

2.25 

325 

Av . 

^34 

2.83 

^34 

2-33 

:22 

2.17 

■.26 

2 

:29 

2-33 

Colored  Sizes. 


G . 

46 

4 

34 

2 

23 

4 

1:05 

8 

42 

4-50 

H . 

59 

4 

40 

2 

29 

4 

I  ;i2 

6 

50 

4.00 

J . 

2 

05 

4 

39 

2 

45 

2 

1:33 

4 

I 

16 

3.00 

L . 

I 

23 

4 

40 

4 

I 

04 

5 

=51 

4 

60 

4-25 

N . 

52 

4 

27 

2 

15 

4- 

■.26 

5 

30 

3-75 

R . 

59 

4 

35 

4 

17 

5 

■.17 

4 

32 

4-25 

Av . 

71 

4 

76 

2.67 

72 

4 

■54 

5-17 

148 

396 

38 


HARVET  ANDREW  PETERSON. 


Colored  Forms. 


' 

1. 

II. 

III. 

IV. 

AVERAGES. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

Time. 

Arrs. 

G . 

24 

2 

19 

2 

33 

4 

25 

4 

25 

3.00 

H . 

22 

3 

36 

2 

24 

2 

22 

4 

26 

2.75 

J . 

45 

2 

I 

15 

5 

37 

2 

22 

2 

45 

2.75 

L . 

35 

2 

45 

2 

38 

3 

38 

3 

39 

2.50 

N . 

16 

2 

13 

2 

16 

3 

15 

2 

15 

2.25 

R . 

15 

3 

13 

2 

1 1 

2 

15 

2 

14 

2.25 

Av . 

:26 

2-33 

=34 

2.50 

:27 

2.67 

:23 

2.83 

■.27 

2.58 

Colored  Forms  of  Different  Sizes. 


G . 

H . 

J . 

L . 

N . 

R . 

20 

48 

43 

28 

20 

16 

2 

2 

2 

2 

2 

2 

:i3 

:46 

I  :io 

:52 

:i6 

:i6 

2 

2 

4 

4 

2 

2 

:4I 

.•46 

=34 

:30 

:25 

:i4 

2 

2 

2 

2 

4 

2 

=43 

;3o 

=38 

=35 

:i5 

.•14 

2 

2 

2 

2 

2 

4 

:29 

43 

:46 

:36 

:i9 

:i5 

2.00 

2.00 

2.50 

2.50 

2.50 

2.50 

Av . 

29 

2 

:36 

2.67 

:32 

2-33 

.■29 

2-33 

:3i 

2-33 

B.  RECALL  AFTER  THIRTEEN  DAYS. 

Colors. 


X. 

Recall. 

IX. 

Recall. 

XXX. 

Recall. 

XV. 

Recall. 

AVER¬ 

AGES. 

Recall. 

G . 

5-25 

11.50 

7.00 

8.50 

8.06 

H . 

7-50 

8.00 

4-50 

7.25 

6.81 

J . 

8.00 

6-75 

4.50 

6.00 

6.31 

L . 

4.50 

7.00 

6.75 

6.00 

6.06 

N . 

6.00 

14.00 

7.50 

4.00 

7.88 

R . 

5-50 

8.25 

8.00 

6-75 

7-13 

Av . 

6.13 

9.25 

6.38 

6.42 

7.05 

Sizes. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  39 


Forms. 


I. 

Recall. 

11. 

Recall. 

III. 

Recall. 

IV. 

Recall. 

AVER¬ 

AGES. 

Recall. 

G . 

11.50 

4.00 

6-75 

8.50 

7.69 

H . 

14.00 

8.00 

5-25 

11.50 

9.69 

J . 

11.50 

4.00 

11.50 

11.50 

9-63 

L . 

11.50 

6.75 

10.00 

9.00 

9-31 

N . 

11.50 

7.00 

10.50 

11.50 

10.13 

R . 

8.25 

5.00 

6.00 

8.00 

6.81 

Av . 

11.38 

5-79 

8-33 

10.00 

8.88 

Colored  Sizes. 


G . 

5.00 

4.00 

6.00 

10.50 

6.38 

H . 

6.50 

5.50 

6.25 

14.00 

8.06 

J . 

11.50 

6.50 

5-50 

8.50 

8.00 

L  . 

5.00 

5-25 

4.00 

4.00 

4-56 

N . 

4.00 

8.25 

8.50 

10.50 

7.81 

R . 

8.25 

9-25 

10.00 

6.00 

8.38 

Av . 

6.71 

6.46 

6.71 

8.92 

7.20 

Colored  Forms. 


G . 

8.00 

6.50 

5.00 

4-75 

6.06 

H . 

14.00 

14.00 

6-75 

10.50 

II. 31 

7-50 

14.00 

5-50 

6.25 

8.31 

L . 

4. 00' 

6.25 

5-75 

7.00 

5-75 

N . 

11.50 

14.00 

6.00 

10.50 

10.50 

R . 

14.00 

5-50 

9.00 

14.00 

10.63 

Av . 

9-83 

10.04 

6.33 

8.83 

8.76 

Colored  Forms  of  Different  Sizes. 


G . 

9.00 

4.75 

10.00 

4-25 

7.00 

H . 

10.50 

8.50 

14.00 

4.00 

9.25 

J . 

8.00 

14.00 

10.50 

6.75 

9.81 

L . 

9.00 

11.50 

4.00 

6.25 

7.69 

N . 

9.00 

5-75 

10.50 

10.00 

8.81 

R . 

11.50 

5.00 

11.50 

6.50 

8.63 

Av . 

9-50 

8.25 

10.08 

6.29 

8.53 

40 


HARVEY  ANDREW  PETERSON 


Table  5.  Areas  varied  in  Color,  Size  and  Form  associated  with  Position. 

Recall  per  Ten  Seconds. 

G. 


COLORS. 

SIZES. 

FORMS. 

COL.  SIZES. 

COL.  FORMS. 

C.  F. 

d.  s. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.V. 

I. 

.719 

.764 

1 .060 

.052 

3  194 

1 .081 

•757 

.258 

2-353 

•705 

3.000 

1. 312 

II. 

2.347 

.864 

•930 

.  182 

.784 

1.329 

.909 

.  106 

2.241 

•593 

1-439 

•249 

III. 

1 . 167 

.316 

•714 

•398 

2.177 

.064 

1-395 

.380 

•943 

•705 

1.639 

.049 

IV. 

1 .700 

.217 

1.742 

.630 

2.297 

.  184 

1 .000 

.015 

1.055 

•593 

•675 

1. 013 

Av. . 

00 

U) 

•540 

I  .  II2 

.316 

2.113 

.665 

1.015 

.  190 

1.648 

.649 

1.688 

.656 

H. 


I. 

.718 

.  104 

2.762 

1.285 

2.233 

.564 

.600 

.202 

2.369 

.486 

1.444 

.115 

II. 

1 . 164 

•342 

1-342 

•135 

1 .071 

•598 

.850 

.048 

2.306 

•423 

1.202 

.  127 

III. 

.685 

•137 

1 . 166 

•311 

.960 

.709 

•797 

.005 

1.386 

•497 

1.938 

.609 

IV. 

.722 

.  100 

•637 

.840 

2.411 

.742 

•959 

•157 

1.470 

•413 

•731 

.598 

Av. 

.822 

.171 

1-477 

•  643 

1.669 

•653 

.802 

.103 

1.883 

•455 

1.329 

.362 

7- 


I. 

.412 

.065 

.506 

.076 

.982 

.  146 

•542 

.062 

.846 

.036 

•924 

•075 

II. 

.625 

.  148 

.267 

.163 

.509 

.619 

•783 

.179 

.760 

.050 

.891 

.  108 

III. 

.  180 

-297 

•393 

•037 

1 .620 

•492 

.620 

.016 

.682 

.  128 

1-353 

•354 

IV. 

.690 

.213 

•554 

.124 

1.402 

■274 

•472 

.132 

•953 

•143 

.827 

.  172 

Av. 

•477 

.181 

■430 

.  100 

1 . 128 

•383 

.604 

.097 

.810 

.089 

•999 

.177 

L. 


I. 

•634 

.029 

1-643 

•531 

1.949 

.322 

.406 

.057 

•727 

.  164 

1.875 

•523 

II. 

.sei 

.201 

I  .  102 

.010 

I  .  125 

.502 

.656 

•193 

.962 

.071 

1-597 

•245 

III. 

.  500 

.163 

.919 

•193 

1.960 

•333 

•351 

.  1 12 

.846 

.045 

.800 

•552 

IV. 

.652 

.oil 

•783 

•329 

1-475 

.152 

.440 

.023 

1 .029 

-138 

1.136 

.216 

Av. 

.663 

.  lOI 

I  .  1 12 

.266 

1.627 

■327 

■463 

.096 

.891 

.105 

1-352 

•384 

INFLUENCE  OF  COMPLEX  ITT  AND  DISSIMILARITF  ON  MEMORY.  41 


N. 


I. 

.689 

.412 

•394 

.083 

1 .402 

•875 

•394 

.652 

2.825 

.246 

2.013 

-174 

11. 

1.728 

.627 

•714 

.238 

1-532 

•745 

1.289 

•243 

3-713 

1-134 

1-413 

.426 

III. 

1 . 165 

.064 

.366 

.110 

2.861 

-584 

I  304 

.258 

1-132 

1-447 

1 .411 

.428 

IV. 

.821 

.280 

.428 

.047 

3-3H 

1-037 

1. 197 

.151 

2.645 

.066 

2-519 

.680 

Av. 

I  .  lOI 

•346 

.476 

.  120 

2.277 

.810 

1 .046 

.326 

2-579 

•723 

1.839 

-427 

R. 


I. 

1.250 

.056 

1.470 

•655 

1.289 

.124 

•833 

.320 

3. Ill 

•235 

3-194 

.902 

II. 

1-473 

.279 

.645 

.  170 

.862 

•551 

1-233 

.080 

1.667 

1.209 

1.389 

•903 

III. 

.909 

•285 

•563 

•252 

1-395 

.018 

1.492 

•339 

2.727 

.149 

3-382 

1 .090 

IV. 

1. 144 

.050 

.580 

•235 

2.105 

.692 

I  053 

.  100 

4.000 

1 . 124 

1 .204 

1 .088 

Av. 

1-194 

.168 

.815 

.328 

1-413 

•346 

I -153 

.210 

2.876 

.679 

2.292 

.996 

SUMMARY. 


COLORS. 

SIZES. 

FORMS. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

G . 

1-483 

•540 

I  .  II2 

.316 

2.II3 

.665 

H . 

.822 

.171 

1-477 

•643 

I  .669 

•653 

J . 

•477 

.181 

•430 

.  100 

1.128 

1-383 

L . 

.663 

.  lOI 

1 . 112 

.266 

1.627 

•327 

N . 

1.115 

•347 

.476 

.  120 

2.277 

.810 

R . 

1-194 

.  168 

.815 

.328 

1-413 

•344 

Av . 

•959 

.251 

.904 

.296 

1.705 

.697 

COL. 

SIZES. 

COL.  FORMS. 

C.  F. 

d.  s. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

G . 

I  .015 

.  190 

I  .648 

.649 

1.688 

.625 

H . 

.802 

.103 

1.883 

•455 

1.329 

.362 

J . 

.604 

.097 

.810 

.089 

•999 

.177 

L . 

•463 

.096 

.891 

.105 

1-352 

•384 

N . 

I  .046 

.326 

2-579 

•723 

1.839 

•427 

R . 

I -153 

.210 

2.876 

.679 

2.292 

.996 

Av . 

•847 

.170 

1 .781 

.450 

1-583 

•495 

42 


HARVET  ANDREW  PETERSON. 


The  results  are  given  in  Tables  4  and  5.  In  part  A  of  Table 
4  the  learning  times  are  given  in  minutes  and  seconds,  and 
arrangements;  in  part  B  the  amounts  recalled  after  thirteen 
days  are  given  on  the  scale  of  14  for  perfect  recall  of  the  series. ‘ 
In  Table  5  the  recall  of  Table  4  is  recalculated  by  finding  the 
equivalents,  in  learning  times,  of  the  arrangements,  adding 
them  to  the  net  learning  times,  and  then  calculating  the  amounts 
recalled  per  ten  seconds  of  aggregate  learning  time.  A  sum¬ 
mary  of  Table  5  follows  it,  and  a  verbal  summary  is  given  last. 
“Rec.”  means  recall  and  M.  V.,  mean  variation. 

Summary  of  results.  For  reasons  evident  in  what  follows  it 
will  be  necessary  to  consider  the  subjects  individually.  It 
may  be  well  to  recall  the  fact  that  we  are  seeking  limits  to  the 
effectiveness  of  increasing  variety,  the  combination  being  each 
time  new,  and  that  from  the  very  nature  of  attention  limits 
will  certainly  be  reached.  It  may  be  well  to  recall  also  that 
with  the  less  varied  bases — the  shades  of  gray  and  violet — all 
of  the  subjects  profited  very  markedly  by  all  of  the  added 
variations.  But  color  is  a  more  varied  base  than  gray  or 
violets  and,  to  say  nothing  of  isolated  series,  a  dozen  series  of 
forms  contains  more  variety  than  a  dozen  series  of  colors. 
Accordingly  it  may  be  expected  that  before  long  the  subjects, 
according  to  their  powers  of  discrimination,  retentiveness,  and 
span  ol  consciousness  and  consequent  ability  to  resist  distrac¬ 
tion,  will  begin  to  diverge.  Some  will  reach  a  limit  sooner  than 
others.  Under  such  conditions,  averages  of  different  subjects 
are  worth  little.  In  w'hat  follows  it  will  be  necessary  to  con¬ 
sider  the  memory  for  size  and  color  separately  as  well  as  in 
combination.  Two  very  important  results  shown  by  all  the 
subjects  in  marked  degree  may  be  mentioned  first,  however. 
First,  all  SIX  subjects  retain  forms  much  better  than  sizes  and 
colors.  Secondly,  all  six  subjects  retain  colored  forms  better  than 
colors.  The  second  of  these  two  results  is  comparable  to  the 
results  obtained  in  the  gray  and  violet  set,  for  in  both  cases 
the  variations  added  were  much  more  easily  discriminated  than 
the  bases  to  which  they  were  added. 


*  Described  on  p.  3 1. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  43 

Subject  G.  Pure  colors  and  pure  sizes  are  retained  about 
equally  well.  Colored  sizes  are  retained  at  least  no  better  than 
either  alone,  while  colored  forms  and  colored  forms  varying  in 
size,  in  themselves  about  equal,  are  not  as  well  retained  as 
pure  forms.  G.  says:^ 

Color  in  colored  sizes  is  a  slight  aid,  but  less  than  the  natural  fluctuation  in 
ease  and  difficulty  in  passing  from  one  size  series  to  another.  In  the  form- 
varying  series,  in  the  long  run  color  is  of  no  value,  unless  there  are  no  peculi¬ 
arities  in  form  or  size  sufficient  to  hold  the  series.  This  seldom  happens. 
The  size  variation  in  colored  forms  of  different  sizes  may  be  of  value  on  occasion. 

Subject  H.  Pure  sizes  are  better  retained  than  pure  colors. 
Colored  sizes  show  no  improvement  over  even  the  poorer  of 
the  two.  Colored  forms  are  slightly  better  retained  than  pure 
forms,  but  the  series  with  two  additions  (color  and  size)  are 
not  as  well  retained  as  pure  forms.  H.  says:  “Colored  sizes 
are  easier  to  learn  than  either  sizes  or  colors,  but  variations 
added  to  form  are  a  distraction  in  learning.  However,  in 
recall  they  may  confirm  the  arrangement  after  it  is  made.” 
H.’s  learning  times  in  Table  4  do  not  confirm  his  remarks  as  to 
the  greater  ease  for  him  of  learning  colored  sizes.  They  took 
more  time. 

Subject  L.  Sizes  are  much  better  retained  than  colors.  Col¬ 
ored  sizes  are  more  poorly  retained  than  either  sizes  or  colors. 
If  the  four  series  of  each  kind  be  arranged  in  order  of  increased 
retention  per  ten  seconds  of  total  learning  time,  all  four  colored 
sizes  are  poorer  than  even  the  corresponding  color  series.  Only 
one  of  the  former  group  is  as  good  as  any  of  the  latter.  Here 
the  combination  is  actually  poorer  than  either  of  the  elements. 
Colored  forms  and  colored  forms  of  different  sizes  are  also 
not  as  well  retained  as  pure  forms.  L.  says: 

Colored  sizes  are  harder  than  colors  and  sizes  because  of  conflicting  methods. 
In  colors  I  associate  the  end  and  middle  colors  with  their  positions,  and  link 

‘  These  opinions  of  the  subjects  were  obtained  in  all  cases  after  all  experi¬ 
menting  had  been  completed.  The  subjects  did  not  know  what  any  of  the 
results  of  the  investigation  were  except  what  they  may  have  inferred  from 
observing  themselves. 


44 


HARVET  ANDREW  PETERSON. 


the  intermediate  ones  with  them  or  with  each  other,  depending  on  the  color 
associations  they  offer.  In  sizes  I  make  groups  of  regularly  increasing  and 
decreasing  sizes. ‘  In  colored  sizes  the  color  distracts  me  from  using  my  size 
method  and  the  size  variations,  from  using  the  color  method.  The  result  is 
I  use  both.  As  a  rule  forms  are  easier  than  colored  forms.  Occasionally  color 
is  an  aid,  for  example  when  the  forms  are  closely  similar.  The  reason  for  the 
difficulty  is  the  same  as  in  colored  sizes,  namely,  conflict  of  habitual  methods. 
Whether  the  addition  of  both  color  andsize  to  form  is  an  aid  I  am  not  sure. 

Subject  N.  Colors  are  much  better  retained  than  sizes, — 
the  reverse  of  the  two  preceding  subjects.  Colored  sizes  are 
retained  better  than  sizes  and  about  the  same  as  colors.  Color 
alone  added  to  form  shows  some  gain  over  pure  form,  but  the 
large  mean  variation  makes  the  advantage  uncertain.  When 
both  color  and  size  variations  are  added,  the  result  is  no  better 
than  in  pure  forms.  N.  says : 

The  color  in  colored  sizes  makes  the  size  stand  out,  but  introduces  a  conflict 
of  methods  of  learning,  and  resulting  distraction.  The  result  is  a  mixture  of 
methods.  I  usually  use  size  to  fix  the  largest  and  smallest  ones  and  color,  and 
size  to  fix  the  intermediate  ones.  The  variations  added  to  form  also  produced 
distraction  in  learning,  the  forms  affording  sufficient  variety  in  themselves. 
T he  color  and  size  variations  added  to  forms  just  gave  me  more  to  notice.  However, 
sometimes  color  aids  in  recalling  the  position  of  a  form. 

With  the  four  persons  above  limits  were  reached.  With 
the  next  two,  however,  they  were  not. 

Subject  y.  Colors  and  sizes  are  retained  about  equally  well, 
and  colored  sizes  are  retained  considerably  better  than  either. 
If  the  series  of  each  group  are  arranged  in  the  order  of  increasing 
retention  per  ten  seconds,  all  of  the  colored  sizes  except  one 
series  are  better  than  the  corresponding  series  of  colors  alone 
or  sizes  alone.  In  the  case  excepted  the  colored  sizes  are  at 
least  as  good.  Colored  forms  and  colored  forms  of  different 
sizes  are  not  quite  as  well  retained  as  pure  forms,  although  the 
difference  is  quite  small.  J.  says: 

The  element  of  color  in  colored  sizes  is  an  aid, — it  gives  each  member  in  the 
series  an  individuality  and  thus  helps  to  fix  it  in  its  absolute  position;  at  the 

*  On  the  methods  of  learning  pure  sizes,  see  p.  48. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  45 

same  time  it  tends  to  break  the  ‘sky-line’  schemes.*  It  is  a  larger  factor  than 
the  natural  fluctuations  in  ease  and  difficulty  of  different  series  of  pure  sizes, 
with  a  few  exceptions.  In  general  all  three  variations  were  aids,  alone  or  in 
combination:  size,  because  it  makes  a  ‘sky-line,’ — to  which  also  forms  may 
contribute;  color  because  it  fixes  the  center,  or  a  term  left  out  of  my  series- 
scheme. 

Subject  R.  Colors  alone  are  better  retained  than  sizes  alone. 
Colored  sizes  are  about  the  same  as  colors.  Both  colored 
forms  and  colored  forms  of  different  sizes  are  considerably 
better  retained  than  pure  forms.  If  the  series  of  each  group 
are  arranged  in  order  of  increasing  retention  per  ten  seconds, 
all  the  colored  forms  and  all  the  colored  forms  of  different  sizes 
exceed  the  corresponding  series  of  pure  forms.  There  seems 
to  be  no  question  that  the  variations  added  to  forms  are  an 
aid  to  this  subject.  She  says: 

The  presence  of  color  in  colored  sizes  is  an  aid  because  it  makes  the  middle 
terms  (middle  in  area)  easier  to  discriminate.  It  does  not  prevent  the  use  of 
the  pure  size  method  (the  method  used  by  all  the  subjects).  The  addition  of 
color  and  size  variations  to  form-varying  series  helps  materially  in  differentiat¬ 
ing  similar  forms  both  in  learning  and  remembering. 

Summary:  To  recapitulate, — four  subjects^  G,  H,  L,  and  N, 
show  practically  no  gain  in  retention  in  either  of  the  two  prin¬ 
cipal  types  of  increased  variation  used  here.  In  quite  a  number 
of  cases  the  recall  is  actually  poorer  with  the  combination. 
The  subjects  are  either  unaffected  by  the  variations,  finding 
sufficient  variety  in  the  base,  or  they  are  distracted  by  a  con¬ 
flict  of  methods  of  learning  which  they  do  not  succeed  in  har¬ 
monizing,  or  by  the  presence  of  variations  which  they  use  only 
occasionally  but  cannot  help  noticing  most  of  the  time.  In 
contrast  with  them  are  the  subjects  y.  and  R.  To  them  all  the 
additional  variations  were  an  aid  subjectively  both  in  learning 
and  recalling,  and  the  tables  quite  decidedly  bear  out  their  intro¬ 
spections  in  the  case  of  colored  sizes  with  y.  and  colored  forms 
and  colored  forms  of  varying  sizes  in  the  case  of  R.  That  a 
type  of  variation  should  be  an  aid  to  J.  and  R.  and  still  not 


*  On  the  method  of  learning  pure  sizes,  see  p.  48. 


+6 


HARVET  ANDREW  PETERSON. 


show  a  gain  in  their  results  is  possible.  It  may  be  too  small 
to  show;  or  it  may  cause  an  unconscious  diminution  in  effort. 
If  a  conflict  of  methods  exists  in  colored  sizes  they  have  har¬ 
monized  it.  This  is  evident  from  the  fact  that  they  use  a 
combination  of  both  methods,  retaining  the  ‘sky-line’  scheme,^ 
and  still  using  color  for  the  terms  intermediate  in  size,  or  for 
a  term  left  out  of  the  size  scheme.  They  are  not  distracted  by 
the  multiplicity  of  variations  in  series  of  the  most  varied  type. 
It  is  interesting  to  note  that  in  natural  retentiveness  and  speed 
of  learning  J.  and  R.  represent  opposite  extremes.^ 

J.  Methods  Employed  by  the  Subjects  in  Learning  the  Series 

Between  the  5th  and  6th  weeks  of  the  regular  work  series 
were  given  for  the  sole  purpose  of  studying  the  subjects’ 
methods.  During  this  week  no  other  series  were  given.  On 
the  introspections  of  these  series,  and  to  a  less  extent  on  those 
given  after  the  final  tests  of  the  regular  series  the  following 
paragraphs  are  based.  They  refer  to  methods  of  learning 
only.  Recall  methods  were  a  survival  of  some  of  the  learning 
methods. 

Fundamentally,  the  subjects  did  not  differ  in  the  methods 
they  employed.  Briefly,  they  all  discriminated  the  terms  of  a 
series  from  each  other,  and  partly  at  the  same  time,  partly 
afterward,  associated  them  with  each  other  and  with  their 
spatial  positions.  The  less  the  terms  differed  from  one  another 
the  more  necessary  it  was  to  differentiate  them.  In  the  two 
series  which  varied  only  in  gray  and  violet,  discrimination 
overshadowed  association,  and  to  the  former  the  long  learning 
times  of  those  series  were  due.  In  series  of  pure  colors  and 
pure  sizes  discrimination  was  easier  and  briefer,  while  in  the 
series  in  which  form  variation  entered,  voluntary  discrimination 
was  at  a  minimum.  It  was  much  more  nearly  instantaneous 
and  involuntary.  As  one  subject  put  it,  ‘discrimination  was 
less  necessary,  because  there  was  not  much  likelihood  that  the 

‘  The  meaning  of  these  conflicts  of  method,  etc.,  will  become  clear  from  the 
discussion  of  the  next  topic. 

^  See  p.  63. 


INFLUENCE  OF  COMPLEXITF  AND  DISSIMILARITT  ON  MEMORY.  47 

terms  would  be  mistaken  for  one  another.’  It  will  be  shown 
in  the  analysis  of  errors  that  with  exceptions  this  remark  was 
true.  The  subjects  came  to  feel  automatically  on  seeing  a  new 
series  whether  there  would  be  in  future  much  or  little  liability 
of  mistaking  one  term  for  another,  and  increased  or  reduced  the 
discrimination  process  accordingly.  Except  in  the  grays,  vio¬ 
lets,  and  pure  sizes,  perceptual  discrimination  in  the  simul¬ 
taneous  exposure  was  easy.  It  was  the  discrimination  in  mem¬ 
ory  which  gave  trouble.  The  other  half  of  the  learning  process, 
the  association,  consisted  in  grouping  the  terms  of  a  series. 
They  might  be  grouped  either  because  they  were  adjacent 
(contiguity),  or  because  they  were  similar.  Discrimination 
itself  was  likely  to  have  impressed  similarities,  because  it  was 
similarity  that  provoked  discrimination.  The  grounds  of  classi¬ 
fication  presented  an  ever-changing  variety.  A  few  of  the  most 
common  will  be  mentioned  in  connection  with  the  particular 
types  of  series,  to  which  we  pass  after  a  word  on  the  subject  of 
language. 

Language  played  small  part  in  learning  and  retaining  the 
series.  Several  subjects  said  that  when  the  forms  and  colors 
were  quite  familiar  they  were  apt  to  suggest  names,  and  one 
said  that  sizes  were  thought  of  by  the  numbers  i  to  7,  but  that 
the  numbers  were  not  run  together  at  all.  This  was  the  sub¬ 
ject  R.  Not  a  single  subject  reconstructed  the  series  from 
language  cues,  according  to  testimony  taken  at  the  close  of 
the  investigation. 

Colors.  The  ends  and  the  middle  were  conspicuous  posi¬ 
tions  with  all  the  subjects.  They  looked  to  see  what  was  there, 
and  if  a  striking  color  was  in  any  one  of  them  it  was  likely  to 
be  made  the  basis  of  a  contiguity  group  or  at  least  make  the 
association  of  the  term  with  its  place  easier.  Other  con¬ 
tiguity  groups  are  illustrated  by  the  introspections:  ‘Red  and 
green  are  complementary  and  in  5th  and  6th  positions,’  ‘blue 
green  is  a  familiar  phrase  and  blue  is  on  the  left  of  green  here.’ 
Some  of  the  similarity  classifications  which  united  non-contigu- 
ous  terms  were:  ‘The  bright  and  the  relatively  colorless  or 
dead  ones,’  ‘the  heavy  and  the  light  ones,’  ‘the  violet  pair,’ 
the  ‘reddish  ones,’  ‘colors  on  the  border-line  between  the 


48 


HARVEY  ANDREW  PETERSON. 


seven  spectral  colors.’  There  was  no  hesitation  in  classing  a 
blue  green  or  a  green  blue,  or  even  the  lighter  tint  of  blue  as  a 
blue  in  one  series  and  a  green  in  another  according  to  the 
exigencies  of  the  situation.  It  is  significant  that  the  recogni¬ 
tion  of  several  colors,  or  sizes,  or  forms  for  that  matter,  as  similar 
was  both  an  aid  and  a  risk, — the  latter  because  it  opened  the  way  to 
subsequent  confusion  of  the  positions  of  the  similar  terms.  Two 
‘blue’  colors  or  two  ‘low’  forms  were  peculiarly  liable  to  exchange 
of  positions.  The  corrective  was  of  course  further  discrimina¬ 
tion.  The  number  of  groups  in  a  color  series  was  necessarily 
relatively  large,  because  the  series  were  constructed  so  as  to  give 
as  much  variety  as  was  compatible  with  keeping  inter-series 
interference  at  a  minimum.  This  number  varied  from  three 
to  five. 

Sizes.  When  in  one  series  the  3d  and  5th  in  size  were  next 
to  each  other,  in  another  the  3d  and  7th,  and  in  another  the 
I  St  and  7th,  and  since  six  such  series  had  been  learned  before  the 
first  two  came  up  for  final  test,  contiguity  could  not  hope  to 
prove  a  successful  method  of  learning  sizes,  and  was  only 
rarely  employed.  Similarity  was  not  used  extensively  if  we 
exclude  such  contrasts  as  smallest  and  largest),  because  it  led  to 
the  confusion  mentioned  in  the  case  of  similar  colors.  All  of 
the  subjects  employed  the  same  method.  They  grouped 
together  a  number  of  terms,  often  not  contiguous,  which  formed, 
abstracting  from  the  intermediaries,  a  continuous  increase  or 
decrease  in  size.  A  variation  of  the  same  method  consisted  in 
remembering  the  length,  direction  and  position  of  the  lines 
running  through  the  tops  of  the  groups.  These  lines  were 
called  ‘sky-lines.’  Some  of  these  ‘systems’  or  schemes  were 
simple  and  natural,  others  complicated  and  natural,  and  quite 
a  number  both  complicated  and  forced.  By  forced  is  meant 
not  true  without  exceptions  so  numerous  that  the  value  of  the 
scheme  must  have  been  slight.  Several  illustrations  of  the 
method  may  be  given. 

Sizes  B.  The  correct  order  was  3416275. ‘  The  subject’s 
system  was  an  ascending  ‘sky-line’  from  ist  to  6th  places,  the 


*  The  numbers  denote  the  relative  size  of  the  terms,  i  representing  the  smallest. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  49 

smallest  and  next  smallest  forming  a  second  ascending  series 
interpolated  in  the  first  at  the  3d  and  5th  positions.  The  last 
term  stood  apart. 

Sizes  A.  The  correct  order  was  5416372.  The  subject’s 
system  consisted  of  three  ‘sky-lines;’  541,  167  and  132. 

One  additional  instance  is  given  to  illustrate  the  fact  that 
subjects  are  not  likely  to  hit  upon  the  same  scheme,  unless  it 
is  very  obvious. 

A  series  of  circles  varying  in  size  and  shade  or  tint  of  red  and 
arranged  in  the  order  3261547  was  given.  One  subject  ob¬ 
served  that  the  smallest  was  in  the  middle  and  the  largest  on 
the  right  end,  that  there  were  two  pairs  which  decreased  in 
size  to  the  right  (32  and  54),  that  4  was  nearest  in  shade  to  7, 
and  that  the  next  largest  was  on  the  left  of  the  middle.  The 
second  subject  agreed  with  the  first,  as  to  the  smallest  and 
largest,  but  his  further  grouping  was  321  and  654,  in  which  two 
groups  the  direction  and  rate  of  decrease  was  the  same,  or  was 
taken  to  be.  The  third  subject  made  a  rightwardly  ascending 
group  out  of  147,  a  rightwardly  descending  group  of  32,  while 
6  was  discriminated  from,  and  thereby  associated  with,  4  which 
it  resembled  in  color.  The  fourth  subject  thought  this  series 
was  easy  for  sizes,  an  opinion  which  the  other  subjects  did 
not  share.  For  her  the  middle  one  was  the  smallest,  while 
each  wing  consisted,  in  order  from  left  to  right,  of  a  medium, 
a  small  and  a  big  one,  with  the  larger  three  on  the  right.  2 
was  discriminated  from  possible  rivals  by  its  color,  and  6  was 
the  one  nearest  7  in  color. 

It  becomes  evident  that  the  schemes  varied  greatly  in  effect¬ 
iveness.  In  the  third  illustration  the  one  used  by  the  last  sub¬ 
ject  was  extremely  good,  while  that  used  by  the  third  subject 
was  poor.  This  fluctuation  in  the  simplicity  and  naturalness 
of  the  systems  explains  the  large  variations  in  the  retention  of 
certain  series  of  pure  sizes  and  colored  sizes  as  compared  with 
the  remaining  series  of  the  same  types  with  the  same  person. 
For  example,  the  unusually  larger  retention  of  Sizes  I  with 
certain  persons  was  due  to  the  discovery  of  the  grouping  45, 
12,  67,  3. 

In  the  colored  sizes  the  variation  in  color  made  the  size 


50 


HARVEr  ANDREW  PETERSON. 


Stand  out  but  it  also  tended  to  check  and  break  up  the  size 
schemes.  The  result  was  a  mixture  of  the  two  methods,  the 
superiority  of  which  to  either  system  alone  the  subjects  were 
not  agreed  upon,  according  to  their  testimony  quoted  in  the 
verbal  summary  of  the  last  table. 

Forms.  Here  again  the  subjects  agreed  in  their  methods,  and 
it  was  substantially  the  same  wherever  form  entered  as  a  varia¬ 
tion.  If  the  color  and  size  varied  also,  these  were  always  sub¬ 
ordinate  means  of  recall.  The  form  was  the  thing,  and  the 
detailed  analysis  of  errors  given  in  the  Appendix  shows  con¬ 
clusively  that  to  the  subject  it  was  the  same  thing  whether  it 
was  large  or  small,  black  or  orange.  Nevertheless,  color  and 
size  variations  were  by  no  means  ignored.  They  entered  as 
secondary  means  of  fixation,  especially  wherever  a  form  was 
similar  to  another  in  the  same  series  or  a  past  series.  Here 
the  subjects  differed  some  according  to  their  own  testimony 
already  given. 

It  is  surprising  that  only  one  subject  in  the  six,  R.,  habitually 
looked  for  resemblances  to  natural  objects  in  the  forms.  There 
had  been  no  instruction  on  this  point. 

Compared  to  the  methods  employed  in  the  series  of  pure 
sizes  and  pure  colors  the  form  method  was  much  more  similar 
to  the  color  method,  but  less  strenuous.  Voluntary  inter-term 
discrimination  was  at  a  minimum  because  it  was  unnecessary. 
The  discrimination  was  involuntary,  immediate  (the  subject 
usually  did  not  hunt  for  it)  and  sensorial  rather  than  logical. 
Here  alone  was  contiguity  grouping  a  leading  and  effective 
method.  The  middle  was  frequently,  though  not  always,  fix¬ 
ated  and  one  or  both  wings  might  then  form  units  consisting 
for  instance  of  a  tall  figure  balanced  by  low  ones  on  either  side 
of  it,  as  in  Forms  B,  and  HI.  The  subjects  repeatedly  said 
that  in  form-varying  series  more  than  elsewhere  they  decided 
doubtful  cases  by  the  appearance  of  the  series  as  a  whole.  Not 
that  they  had  an  image  of  the  appearance  of  the  series.  Rather 
certain  arrangements  tentatively  made  did  not  look  right.  In 
this  feeling  they  were  more  often  right  than  wrong.  Esthetic 
considerations  were  prominent  in  series  varying  in  form  or 
color,  but  discord  was  as  effective  a  vivifier  as  harmony. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  51 


Analysis  of  Errors. 

For  a  detailed  and  probably  more  enlightening  account 
of  all  the  errors  made  by  two  subjects,  N.  and  R.,  pages  80-7 
should  be  consulted.  A  general  summary  of  the  errors  of 
all  the  subjects  will  be  sufficient  here.  Two  types  of  errors 
are  distinguishable:  confusion  and  simple  fading  out.  By 
confusion  is  meant  all  cases  where  the  subject’s  arrange¬ 
ment  has  wrongly  followed  an  arrangement  in  some  other 
series  or  in  another  part  of  the  present  series,  because  of 
some  similarity  in  color,  size,  form,  or  what  not.  The  confu¬ 
sion  need  not  be  mental.  Quite  as  often  it  is  purely  physio¬ 
logical,  as  will  be  noticed  below.  We  shall  class  all  errors  not 
due  to  confusion  as  due  to  fading.  An  extreme  case  of  fading 
is  the  following:  A  young  man  who  had  recently  spent  five 
years  in  the  tropics  was  conscious  that  his  mental  processes 
had  become  sluggish,  and  his  memory  less  impressionable. 
On  the  second  morning  of  work  in  our  experiment,  although 
only  one  series  of  a  kind  had  been  learned  the  day  before,  and 
only  three  in  all,  he  said,  when  the  duplicates  of  some  of  the 
series  were  laid  before  him,  that  if  he  had  been  shown  that 
series  the  day  before,  he  was  not  aware  of  it!  Our  classification 
is  the  result,  however,  of  the  detailed  analysis  of  errors.  The 
two  types  are  not  meant  to  be  mutually  exclusive,  but  only  to 
define  predominant  characteristics.  It  is  true  that  confusion  is 
apt  to  occur  only  after  a  certain  amount  of  fading  has  taken 
place. 

In  the  series  of  sizes,  colors  and  colored  sizes  the  type  of  error 
which  we  have  called  confusion  is  overwhelmingly  the  prepon¬ 
derant  type.  In  the  earlier  series  of  colors  the  subject  associates 
certain  colors  with  certain  positions.  In  later  color-varying 
series  he  has  to  associate  with  the  same  positions  colors  which 
in  memory  at  least  he  does  not  distinguish  from  the  earlier 
ones.  Interference  arises,  which  is  more  often  not  noticeable 
at  the  time  of  learning,  if  the  learnings  occur  on  different  days, 
but  which  becomes  marked  in  recall  after  twenty-four  hours, 
and  still  more  marked  after  two  weeks.  With  the  accumula¬ 
tion  of  series  in  which  the  color  varies,  recollection  in  the  final 


52 


HARVET  ANDREW  PETERSON. 


test  becomes  worse.  The  interference  may  or  may  not  be 
mental.  It  frequently  is  so,  but  on  the  other  hand  if  the  sub¬ 
ject  is  following  an  arrangement  in  another  similar  group  (sim¬ 
ilar  in  almost  any  respect),  he  is  apt  to  feel  quite  sure  that  he 
is  correct.  After  a  number  of  color-varying  series  the  subject 
is  apt  to  say  when  trying  to  recall  their  order  in  a  final  test 
that  the  colors  look  about  as  well  in  one  place  as  in  another. 
By  this  he  means  that  colors  which  he  has  classed  as  yellow, 
for  example,  have  stood  in  a  good  many  different  positions, 
and  he  is  uncertain  which  one  this  yellowish  term  belongs  in. 
Exchange  of  colors  in  the  same  series  is  not  as  common  as 
confusion  of  different  series,  because  in  construction  the  colors 
were  intentionally  varied;  still,  it  does  occur,  for  example 
when  two  or  more  colors  have  been  grouped  on  account  of  a 
common  property  not  reckoned  with  by  the  operator,  as  dull¬ 
ness,  brightness,  complementariness,  togetherness  in  the  sub¬ 
ject’s  past  experience.  We  have  had  occasion  before  to  speak 
of  intellectual  classifications  as  a  cause  of  confusion  of  position 
when  not  followed  by  further  discrimination. 

In  series  of  sizes  and  colored  sizes  confusion  of  terms  within 
the  same  series  is  much  more  frequent  than  in  colors.  This 
means  the  sizes  are  less  discriminable  perceptually.  Confusion 
of  one  series  with  another  may  occur  within  the  same  half 
hour  (for  example,  pure  sizes  with  colored  sizes),  and  is  more 
marked  with  longer  intervals.  On  the  second  and  third  day 
of  learning  the  subject  may  be  aware  of  it  and  correct  it  partly 
or  wholly.  Or  he  may  be  unconscious  of  it.  The  different 
types  of  situations  are  the  same  as  described  above  for  colors. 
It  has  frequently  happened,  however,  that  a  size-varying  series 
has  been  arranged  in  a  final  test  in  the  order  of  some  other 
series  with  entire  correctness,  and  still  the  subject  was  not 
aware  of  the  mistake  in  identity!  This  has  never  happened 
with  colors  or  with  form-varying  series,  and  is  an  evidence  of 
the  high  degree  of  unity  of  the  size-varying  series,  especially 
pure  sizes.  In  this  respect  they  are  the  equal  of  form-varying 
series.  This  is  due  to  the  ‘sky-line’  and  mass-group  systems 
used  in  such  series,  and  described  above  in  connection  with 
the  methods  of  learning.  The  absence  of  errors  of  the  fading 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY.  53 

out  type  in  sizes  is  striking.  Almost  all  of  the  errors  made  dur¬ 
ing  learning  were  exchanges  of  sizes  nearest  each  other  in  area, 
or  nearest  but  one.  Proof  of  this  in  the  form  of  a  quantitative 
statement  is  given  on  pp.  61-62  in  connection  with  some 
experiments  similar  to  these,  and  it  is  also  shown  very  con¬ 
clusively  in  less  convenient  form  in  the  detailed  analysis  of 
the  errors  of  R.  and  N.  in  the  present  experiment,  to  be  found 
on  pp.  80-7. 

In  series  in  which  form-variation  enters  confusion  is  rela¬ 
tively  much  less  frequent  than  in  colors,  sizes  and  colored  sizes, 
and  fading  out  is  more  common,  the  total  number  of  errors 
being  also  much  less.  Exchange  of  adjacent  terms,  or  inver¬ 
sion,  IS  the  most  frequent  error.  It  is  due  to  not  noticing  the 
individual  terms  closely  enough  (insufficient  discrimination). 
The  subject  relies  on  his  sensory,  non-logical  impression,  at 
the  point  where  the  error  later  occurs.  This  is  adequate  for 
the  test  which  follows  immediately  after  learning,  but  by  the 
next  day  many  of  these  details  have  faded  out.  We  agree 
with  Ranschburg  that  this  type  of  error  is  relatively  unimpor¬ 
tant  for  studying  the  effects  of  similarity,  because  it  is  not  a 
similarity  type  of  error.  However,  confusion  is  by  no  means 
absent  from  form-varying  series.  Confusion  of  terms  within 
the  same  series  seldom  occurs.  Inspection  of  the  plates  shows 
why.  But  the  single  re-using  of  an  old  form,  or  the  occurrence 
of  forms  which  generically  are  the  same,  for  instance  two  vases, 
crosses,  figures  whose  general  contour  is  triangular,  etc., 
produces  interference  and  confusion,  the  more  striking  only 
because  it  can  be  identified  with  more  certainty,  on  account  of 
the  individuality  of  forms.  The  poor  average  recall  of  Forms 
II,  Col.  Forms  III,  and  C.  F.  d.  S.  IV,  and  the  individually 
poor  recalls  of  N.  and  R.  in  C.  F.  d.  S.  II  are  due  to  the  re-using 
of  old  forms. ^ 


N.  and  R.  took  the  places  of  F.  and  Mc.P.  in  the  experiment  and  learned 
the  series  in  a  somewhat  different  order  from  the  one  followed  by  the  four 
other  subjects. 


54 


HARVET  ANDREW  PETERSON. 


5.  Other  Experiments  with  the  Same  Bases 

Association  with  Temporal  Order  and  with  Numbers.  In 
the  last  set  of  experiments,  limits  to  the  benefit  of  increasing 
the  complexity  in  the  direction  of  dissimilarity  were  found  for 
four  subjects  at  the  level  of  pure  colors  and  pure  forms.  The 
combination  of  color  and  size,  themselves  equal  in  difficulty, 
was  no  better  than  either  alone;  nor  were  the  additions  of 
color  and  size  variations,  in  themselves  poorer  than  forms, 
when  added  to  forms,  an  aid.  With  two  other  subjects,  how¬ 
ever,  the  combinations  were  better  than  the  variations  singly. 
With  them  the  limits  lie  in  some  further  increase  in  complexity. 
We  might  have  experimented  with  these  two  subjects  further, 
adding  still  more  variations  to  the  same  bases,  or  using  more 
variable  bases  than  colors  and  forms.  Inviting  as  this  was, 
we  preferred  to  test  the  generality  of  the  conclusion  that  a 
limit  is  to  be  expected  with  any  subject  on  the  level  of  pure 
colors  and  pure  forms.  This  we  did  by  repeating  the  experi¬ 
ments  with  new  subjects,  successive  exposure  and  association 
of  the  colors  and  forms  with  other  associates  than  spatial 
position. 

The  24  series  used  in  the  foregoing  section  were  given  to 
one  new  subject  with  successive  instead  of  simultaneous  expo¬ 
sure,  and  he  was  required  to  associate  each  term  with  its  tem¬ 
poral  position  in  the  series.  The  cardboard  screens,  which 
stood  between  the  aperture  through  which  the  subject  looked 
and  the  carriage  by  which  the  series  were  moved,  were  nar¬ 
rowed  so  as  to  expose  only  one  term  at  a  time.  The  series  were 
entirely  remounted  for  successive  exposure  on  cardboard  sheets, 
II  inches  high  and  42  inches  or  more  long.  Instead  of  having 
all  the  terms  rest  on  a  base  line,  the  middle  points  in  the  ver¬ 
tical  diameters  of  the  terms  were  placed  on  a  line  running  the 
length  of  the  sheet,  midway  between  the  lower  and  upper 
margins.  When  a  form  arranged  in  this  way  appeared  top- 
heavy,  it  was  lowered  until  the  unpleasant  effect  disappeared. 
No  fixation  point  was  enforced.  All  of  the  conditions  under 
which  the  previous  series  were  given  as  to  avoiding  names, 
reviewing,  use  of  duplicates  to  show  the  learner’s  progressive 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  55 

mastery  of  the  series,  the  requirement  that  the  series  be  held 
perfectly  for  24  hours  before  the  learning  was  discontinued, 
were  maintained  here.  The  only  changes  were  successive  expo¬ 
sure,  final  test  after  6  days  instead  of  13  and  arrangement  of 
the  duplicates  by  the  subject  in  their  temporal  instead  of 
spatial  order.  The  interval  before  the  final  test  was  shortened 
because  successive  exposure  made  the  task  more  difficult.  In 
the  various  tests  the  subject,  as  before,  did  not  see  the  dupli¬ 
cates  until  the  exposure  was  over.  He  then  uncovered  them 
and  arranged  them  in  their  time  sequence,  one  on  top  of  the 
other,  face  down.  Six  series,  one  of  each  kind,  were  given 
each  week.  The  subject  worked  on  four  successive  days  each 
week  and  a  fifth  if  necessary  to  bring  the  series  up  to  stand¬ 
ard.  Four  new  series  were  begun  the  first  day  and  the  remain¬ 
ing  two  on  the  second  day.  The  rate  of  exposure  was  50 
strokes  of  the  metronome  per  minute  with  an  exposure  on 
each  alternate  stroke.  A  term  was  thus  exposed  about  1.2 
seconds.  The  subject  regulated  the  number  of  repetitions  of 
the  series  which  he  took,  but  less  than  a  repetition  of  the  whole 
series  was  never  given.  Thus  the  measure  of  the  rapidity  of 
learning  was  the  number  of  repetitions  and  arrangements 
required  to  bring  the  series  up  to  perfect  retention  after  24 
hours.  The  following  table  gives  the  results.  The  figures  on 
the  left  and  right  sides  of  the  dashes  give  the  number  of  repe¬ 
titions  and  arrangements  respectively  required  to  learn  the 
series;  the  figures  under  them  give  the  amount  recalled  in  the 
final  test,  14  being  a  perfect  score.  In  the  lower  half  of  the 
table  the  same  recall  is  recalculated  per  repetition  of  learning, 
after  reducing  arrangements  to  their  equivalents  in  number  of 
repetitions.  This  equivalent  was  found  by  special  experiments 
given  for  the  purpose  in  the  same  manner  as  for  the  subjects 
of  the  preceding  group  of  experiments.^ 


^  See  pp.  65-7. 


56 


HARVET  ANDREW  PETERSON. 


Fable  6.  Areas  varied  in  Color,  Size  and  Form  associated  with  Time 

Position. 

Subject  U. 


COLORS, 

SIZES. 

I. 

II. 

III. 

IV. 

I. 

II. 

ni. 

IV. 

4-2 

4-4 

4-2 

6-3 

6-4 

1 1-8 

7-4 

6-3 

5-25 

3-50 

5-50 

4.00 

8.25 

11.25 

5.50 

6.50 

FORMS. 

COLORED  SIZES. 

3-4 

4-4 

3-2 

2-2 

6-4 

4-4 

6-4 

4-3 

8-75 

5-25 

11.50 

10.00 

5.00 

5.00 

6.50 

4.00 

COLORED 

FORMS. 

C.  F, 

d.  s. 

6-4 

3-4 

2-2 

3-4 

3-2 

2-2 

3-2 

4-3 

11.50 

14.00 

6.50 

14.00 

11.50 

9.00 

7.00 

8-75 

Recall  per  Repetition. 


Series. 

COLORS. 

SIZES. 

FORMS. 

Rec. 

M.  V. 

Rec. 

M.V. 

Rec. 

M.  V. 

I . 

•715 

.176 

.650 

.  122 

•903 

.046 

II . 

•327 

.212 

.472 

.056 

.491 

•458 

Ill . 

•749 

.210 

.402 

.  126 

I.811 

.862 

IV . 

•363 

.  176 

•589 

.061 

•589 

.360 

Av . 

•539 

.194 

.528 

.091 

•949 

•432 

Series. 

COL.  SIZES. 

COL.  FORMS. 

C.  F, 

d.  s. 

Rec. 

M.V. 

Rec. 

M.V. 

Rec. 

M.V. 

I . 

•394 

.060 

.906 

•347 

1.812 

.420 

II . 

.468 

.014 

1-445 

•5.39 

1.683 

.291 

Ill . 

.512 

.058 

1-215 

.038 

1. 103 

.289 

IV . 

•443 

.01 1 

1-445 

•539 

0 

O' 

.422 

Av . 

•454 

•034 

1-253 

.366 

1.392 

•356 

INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  57 

A  study  of  Table  6  shows  that  colors  and  sizes  are  remem¬ 
bered  about  equally  well  and,  as  usual,  forms  better  than 
either.  The  combination  of  color  and  size  is  not  as  effective 
as  either  separately,  but  both  colored  forms  and  colored  forms 
of  different  sizes  are  more  effective  than  forms  alone. 

With  the  subject  U.  and  two  new  subjects,  W.  and  X.,  the 
same  24  series  were  next  associated  with  the  numbers  2  to  8. 
The  same  seven  numbers  were  used  in  every  series.  They 
took  the  place  of  the  seven  spatial  and  seven  temporal  posi¬ 
tions.  Certain  substitutions  were  also  made  in  the  series  of 
pure  forms,  the  result  of  which  was  that  no  form  was  used 
twice  in  all  the  form-varying  series.  This  was  effected  by 
substituting  Forms  A  and  B  for  Forms  III  and  IV,  and  the 
alternative  figures  called  B  in  the  plates  for  those  of  the  same 
number,  e.  g..  Fig.  6B  was  substituted  for  Fig.  6.  Naturally 
the  order  of  presenting  the  terms  was  frequently  changed  to 
prevent  the  entrance  of  position  associations.  The  numbers 
were  of  a  large,  fairly  heavy  style,  16  mm.  high.  Nos.  3,  4,  6 
and  7  were  black  and  2,  5  and  8  were  red,  to  reduce  the  labor 
of  learning, — an  application  of  the  advantage  of  variety  to 
our  own  experiment.  The  series  in  the  form  in  which  they 
had  been  arranged  for  U.  were  used,  and  the  numbers  were 
pasted  on  the  centers  of  the  terms.  Where  a  term  had  been 
lowered  for  aesthetic  reasons  the  number  was  put  on  the  hori¬ 
zontal  axis  of  the  series,  equally  distant  from  the  right  and 
left  sides  of  the  term.  The  altered  orders  used  to  prevent 
position  association  were:  1st  rep.,  1234567;  2nd  rep.,  2134567, 
3d  rep.,  1235746,  4th  rep.  1234576,  then  if  more  repetitions 
were  necessary,  the  same  order  over  again.  In  the  tests  the 
subject  took  a  set  of  duplicate  numbers  mounted  on  circular 
microscope  slide  covers  and  placed  them  on  his  duplicate  set 
of  terms.  All  of  the  other  conditions  were  the  same  as  for 
the  subject  U.,  as  described  above.  With  X.  the  interval 
between  the  completion  of  learning  and  the  final  test  was 
reduced  to  3  days,  because  a  greater  interval  was  too  long  to 
produce  sufficient  recall.  U.  was  used  again  in  this  experiment, 
mainly  because  his  time  was  at  our  disposal.  This  was  a 
divergence  from  the  fundamental  assumption  of  our  problem. 


58 


HARVET  ANDREW  PETERSON. 


namely  that  the  combination  of  variations  must  not  already 
have  formed  a  unity  in  the  subject’s  past  experience.  While 
he  had  not  associated  numbers  with  the  series,  the  combina¬ 
tions  of  color,  form  and  size  were  not  wholly  unfamiliar  to 
him.  Nevertheless,  his  results  present  no  important  difference 
from  his  previous  work  or  from  the  results  of  the  other  subjects, 
and  they  are  consequently  included. 

The  results  of  this  experiment  are  given  in  Table  7.  The 
numbers  on  the  left  and  right  of  the  dashes  give  the  number  of 
repetitions  and  arrangements  respectively  required  to  bring  the 
series  up  to  standard,  the  numbers  under  them,  the  terms 
correctly  associated  after  three  days  for  X.  and  six  days  for  U. 
and  W.  There  were  seven  couplets  in  a  series  and  a  score 


Table  7 — T.  Areas  varied  in  Color,  Size  and  Form,  associated  with  Numbers. 


COLORS. 

SIZES. 

I. 

II. 

III. 

IV. 

I. 

II. 

III. 

IV. 

u . 

6-3 

8-4 

5-6 

3-2 

6-6 

9-7 

3-2 

6-9 

5 

5 

2 

4 

5 

5 

I 

5 

w . 

8-2 

5-3 

5-2 

4-2 

5-5 

7-3 

7-4 

9-7 

7 

3 

3 

2 

2 

I 

5 

5 

X . 

10-6 

17-5 

lO-II 

22-11 

9-7 

00 

1 

10-5 

7-6 

0 

I 

5 

3 

2 

0 

3 

5 

FORMS. 

COLORED  SIZES. 

u . 

6-6 

9-6 

2-2 

4-6 

6-4 

5-4 

4-3 

3-4 

7 

5 

4 

7 

4 

5 

3 

5 

w . 

4-2 

5-3 

5-2 

6-4 

4-3 

9-4 

6-2 

5-2 

7 

7 

7 

7 

2 

7 

2 

5 

X . 

6-4 

4-4 

6-6 

7-9 

9-6 

14-10 

5-3 

10-7 

3 

3 

3 

7 

3 

7 

I 

7 

COLORED  FORMS. 

C.  F. 

d.  s. 

u . 

3-2 

4-4 

3-2 

2-3 

6-4 

4-4 

4-5 

2-2 

7 

5 

7 

5 

7 

7 

5 

6 

w . 

6-4 

6-4 

5-2 

5-4 

4-2 

5-4 

4-2 

4-2 

7 

5 

4 

7 

3 

7 

7 

7 

X . 

5-5 

3-2 

3-3 

7-4 

6-6 

3-4 

3-4 

3-2 

4 

3 

7 

5 

3 

5 

7 

3 

INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  59 


Table  7. — B.  Areas  varied  in  Color,  Size  and  Form,  associated  with  Numbers. 

Recall  per  Repetition. 

u. 


COLORS. 

SIZES. 

FORMS. 

COL.  SIZES. 

COL.  FORMS. 

C.  F. 

d.  s. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

1. 

•453 

.062 

•305 

.060 

•436 

.050 

•315 

.083 

1 . 103 

•256 

•552 

•I31 

II. 

•347 

.044 

.241 

.006 

.262 

.224 

•427 

.029 

.468 

•379 

•655 

.028 

III. 

.132 

.259 

.156 

.079 

•747 

.261 

•332 

.066 

1. 103 

.256 

.404 

•279 

IV. 

.630 

•239 

•237 

.002 

.498 

.012 

.516 

.118 

.712 

•135 

I  .  I2I 

•438 

Av. 

•391 

•I51 

•235 

•037 

.486 

•137 

•398 

.074 

.847 

•257 

.683 

.219 

w. 


I. 

.875 

.231 

0 

0 

•053 

1-750 

.321 

.500 

•153 

1 . 167 

.117 

•750 

.663 

II. 

.600 

.044 

•143 

.310 

1 .400 

.029 

•777 

•134 

•833 

.217 

1 .400 

•013 

III. 

.600 

.044 

.714 

.261 

1 .400 

.029 

•333 

.320 

.800 

.250 

1-750 

•3.37 

IV. 

.500 

.144 

•555 

.  102 

1 . 167 

.262 

1 .000 

•347 

1 .400 

•350 

1-750 

•337 

Av. 

.644 

.116 

•453 

.182 

1.429 

.  160 

•653 

•277 

1.050 

•234 

1-413 

•338 

X. 


I. 

.000 

.055 

•073 

•033 

.182 

.006 

.  121 

•049 

.221 

.158 

•138 

.210 

II. 

•033 

.022 

.000 

.  106 

.207 

.019 

•232 

.062 

•365 

.014 

•371 

.023 

III. 

.128 

•073 

.  129* 

.023 

•138 

.050 

.078 

.092 

.645 

.266 

•519 

.171 

IV. 

•059 

.004 

.220* 

.114 

.226 

•038 

•247 

•077 

.286 

•093 

•364 

.016 

Av. 

•055 

•039 

.  106 

.069 

.188 

.028 

.  170 

0 

0 

•379 

•133 

•348 

.105 

*  Memorized  order  of  numbers  only. 


Summary  of  Part  B. 


COLORS. 

SIZES. 

FORMS. 

COL. 

SIZES. 

COL.  FORMS. 

c.  r. 

d.  s. 

Rec. 

M  .V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

Rec. 

M.  V. 

U . 

•391 

.151 

•235 

•037 

.486 

•137 

•398 

•074 

.847 

.321 

.683 

.219 

W . 

.644 

.116 

•453 

.  182 

I  .429 

.  lOI 

•653 

.211 

1.050 

•234 

1-413 

•338 

X . 

•055 

•039 

.  106 

.069 

.188 

.028 

.  170 

.040 

•379 

•133 

•348 

.105 

Av.... 

•363 

.  102 

.265 

.096 

.701 

.089 

.407 

.  108 

•759 

.229 

.815 

.221 

6o 


HARVET  ANDREW  PETERSON 


of  I  was  allowed  for  each  correct  association,  with  no  partial 
credits.  Part  B  of  the  same  table  gives  the  same  recall  per 
repetition,  after  calculating  in  the  equivalents  of  the  arrange¬ 
ments*  in  terms  of  learning  time  according  to  the  method 
described  on  pp.  65-7,  A  numerical  summary  follows  the 
table  and  a  verbal  summary  is  given  last. 

Summary.  Two  of  the  subjects  do  considerably  better  with 
colors  than  with  sizes,  while  the  third,  X.,  does  not  recall 
enough  of  either  for  comparison.  For,  as  indicated  in  a  foot¬ 
note  to  Table  7,  part  B,  he  learned  only  the  numbers  in  Sizes 
III  and  IV.  During  learning  he  mentally  arranged  the  num¬ 
bers  in  the  order  which  they  would  have  if  the  sizes  had  been 
exposed  in  the  order  from  smallest  to  largest.  These  two 
series  should  therefore  perhaps  not  be  counted.  All  three 
subjects  do  markedly  better  with  forms  than  with  sizes  and 
colors.  With  U.  and  W.  colored  sizes  are  not  better  than  color 
alone,  but  size  is  substantially  improved  by  the  addition  of 
color  as  would  be  expected.  But  with  X.  colored  sizes  are 
much  better  than  either  color  or  size  alone.  This  is  confirmed 
unqualifiedly  by  the  introspections  of  the  subject.  For  him 
pure  colors  or  sizes  were  almost  impossible  after  the  first  series 
of  each,  partly  on  account  of  their  inherent  difficulty,  but 
more  because  of  the  interference  of  past  associations.  He 
made  in  memory  few  if  any  more  color  discriminations  than 
the  seven  of  the  spectrum.  With  U.  colored  forms  and  colored 
forms  of  different  sizes  are  both  more  effective  by  considerable 
amounts  than  forms  alone, — an  outcome  which  duplicated  his 
records  in  the  associations  with  temporal  order.  The  subject 
X.  also  profits  by  the  increased  complexity  in  both  cases, — colored 
forms  and  colored  forms  of  different  sizes.  His  recall  is  prac¬ 
tically  doubled  in  both  cases,  compared  with  pure  forms. 
Here  again  the  introspections  confirmed  the  results.  W.  on 
the  contrary  is  not  benefited  by  the  additions  to  form.  Colored 
forms  are  even  poorer.  It  is  interesting  to  note  that  the  three 
subjects  differed  very  widely  in  natural  retentiveness,  that  the 
one  who  remembered  the  least  profited  the  most  from  increased 
variety,  while  the  one  who  remembered  the  most  did  not  profit 
by  the  additions  in  any  case.  U.  occupies  a  middle  place  in 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY.  6 1 


respect  both  to  natural  retentiveness  and  the  use  made  of  the 
additional  variations.  When  asked  at  the  close  of  the  inves¬ 
tigation  whether  the  presence  of  color  and  color-size  variations 
in  the  form-varying  series  was  a  help,  as  constrasted  with  pure 
forms,  W.  replied,  “Only  occasionally,  when  the  forms  are 
similar.  As  a  rule  I  find  sufficient  variety  in  the  form  alone.” 
And  yet  she  did  not  take  the  forms  to  be  copies  of  objects, 
except  in  the  most  obvious  cases.  They  were  simply  colored 
areas.  On  the  other  hand  X.  looked  for  resemblances  to 
objects  constantly,  and  found  them  usually. 

The  distribution  of  the  benefit  of  increased  variety  is  the 
same  as  we  have  found  before.  The  learning  time  is  shortened 
and  still  the  amount  recalled  after  a  week  is  greater.  U.  learns 
forms  in  an  average  of  5.25  reps,  and  5  arrs.,  colored  forms 
in  3  reps,  and  2.75  arrs.,  and  colored  forms  of  different  sizes 
in  4  reps,  and  3.75  arrs.  His  average  recalls  are  5.755  ^  and 
6.25  terms  respectively.  X.  learns  colors  in  an  average  of 
14.75  reps,  and  8.25  arrs.,  sizes  in  8.50  and  5.75,  colored  sizes 
in  9.50  and  6.50.  His  average  recalls  are  2.25,  2.50  and  4.50, 
respectively.  He  learns  forms  in  5.75  reps,  and  5.75  arrs., 
colored  forms  in  4.50  reps,  and  3.50  arrs.,  colored  forms  of 
different  sizes  in  3.75  reps,  and  4  arrs.  His  average  recalls 
are  4,  4.75  and  4.50. 

The  results  with  these  three  subjects  simply  confirm,  and 
extend  the  conclusion  reached  with  the  six  subjects.  The 
change  to  successive  exposure  and  a  different  association  has 
shown  no  change  in  the  conditions  of  learning  nor  in  the  results. 
After  a  brief  treatment  of  two  somewhat  different  topics  in 
the  next  three  sections,  the  results  of  the  whole  investigation 
will  be  brought  together  in  the  Conclusion. 

(5.  Analysis  of  Errors. 

In  the  24  simultaneous  series  begun  in  V  2,  it  was  found 
that  in  colors,  sizes  and  colored  sizes,  confusion  was  quite 
decidedly  the  most  frequent  cause  of  error,  and  the  detailed 
analysis  of  R.’s  and  N.’s  errors  would  have  shown  that  both 
of  the  possible  kinds  of  interference,  namely  of  terms  within 


62 


HARVEY  ANDREW  PETERSON. 


the  same  series,  and  of  different  series  with  each  other,  were 
equally  prominent.  In  the  present  experiments  successive  ex¬ 
posure  made  single  schemes  for  the  whole  of  a  series  prac¬ 
tically  impossible  and  the  influence  of  past  series  became  less. 
Memorizing  became  much  more  a  couplet  affair.  The  inter¬ 
ference  in  the  series  of  sizes  and  colored  sizes  particularly  was 
almost  wholly  traceable  to  terms  in  the  same  series,  as  shown 
in  the  following  summary,  in  which  is  included  every  error 
made  in  all  the  series  in  which  there  were  three  errors  or  less. 
It  includes  U.’s  temporal-order  series  and  U.’s  and  X.’s  num¬ 
ber  association  series. 


Sizes  and  Colored  Sizes. 


SUBJECT 

KIND  OF  ASSOCIATION. 

NEAREST 

SIZES. 

NEAREST 

SIZES  BUT 

ONE. 

ALL 

OTHERS. 

TOT.AL. 

U . 

Temporal  Order . 

8 

4 

2 

14 

u . 

Number  Associations . 

21 

4 

0 

X . 

Number  Associations . 

17 

5 

4 

26 

Total . 

46 

13 

6 

65 

By  nearest  sizes  is  meant  sizes  nearest  each  other  in  area. 
These  sizes  were  simply  mistaken  for  each  other.  In  the  next 
summary  the  proof  is  less  certain  only  because  color  similarity 
cannot  be  so  objectively  defined.  Its  definition  is  due  to  the 
opinion  of  the  experimenter,  aided  by  a  Bradley  Color  Book. 
We  included  in  our  definition  only  colors  obviously  similar  in 
perception,  and  therefore  quite  certainly  took  a  narrower  defi¬ 
nition  than  the  limits  within  which  colors  would  seem  similar 
in  memory. 


Colors. 


SUBJECT 

KIND  OF  ASSOCIATION. 

SIMILAR 

COLORS. 

NOT 

SIMILAR 

COLORS. 

TOTAL. 

U . 

Temporal  Order . 

2 

0 

2 

u . 

Number  Associations . 

4 

2 

6 

X . 

Number  Associations . 

1 1 

2 

13 

Total . 

17 

4 

21 

INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  63 

In  the  form-varying  series  of  the  temporal  order  set  of  U., 
inversion  of  adjacent  terms  was  the  most  common  error,  which 
result  agrees  with  those  of  the  corresponding  spatial  position 
associations.  Of  the  22  errors  made  in  all  the  series  in  which 
3  errors  or  less  occurred,  15  were  exchanges  of  adjacents,  4 
were  due  to  similarity  in  form  and  3  to  no  assignable  cause. 
Of  the  form-varying  series  of  the  number  associations  the  only 
statement  that  can  be  made  is  that  confusion  due  to  similarity 
was  less  frequent  than  in  the  series  of  sizes  and  colors.  Inver¬ 
sion  of  adjacents  is  here  not  a  possible  type  of  error  on  account 
of  changes  of  the  order  in  learning. 

VI.  INDIVIDUAL  DIFFERENCES  IN  SPEED  OF  MEMORIZING  AND 

IN  RETENTIVENESS 

If  the  differences  in  material  be  disregarded,  the  experiments 
described  in  V  2  give  results  from  six  subjects  with  the  same 
24  series.  Since  all  of  them  were  required  to  learn  the  series 
in  the  same  way  we  may  compare  the  subjects  simply  as  learners. 
The  three  subjects  used  in  the  experiments  with  numbers  can¬ 
not  be  compared  with  the  first  six  only  among  themselves. 
The  following  table  is  compiled  from  the  averages  for  the 
different  persons  given  in  Tables  4  and  7.  Part  A  below 
gives  on  the  left  the  average  number  of  seconds  which  each 
of  the  first  six  subjects  required  to  bring  the  series  up  to  the 
point  where  he  had  held  its  arrangement  perfectly  for  a  day. 
On  the  right  side  are  given  the  average  amounts  recalled, 
marked  on  a  scale  of  14.  In  part  B  similar  averages  are  cal¬ 
culated  for  the  three  subjects  in  the  experiment  with  numbers. 
These  figures  also  are  based  on  24  series  and  the  amount 
recalled  is  based  on  a  scale  of  7.  The  subjects  are  arranged  in 
order  of  speed  of  learning  and  amounts  recalled. 


64 


HARVEY  ANDREW  PETERSON. 


Table  8. 
Part  A. 


SUBJECTS. 

TIME. 

ARRS. 

SUBJECTS. 

AMOUNT 

RECALLED. 

R . 

22 

317 

3-42 

325 

2.88 

H . 

Q.  16 

N . 

26 

N . 

8.31 

8.02 

G . 

33-5 

28.8 

46.7 

60.2 

T . 

H . 

J 

R . 

7.64 

6.97 

6.92 

L . 

2.92 

2.92 

G . 

T . 

L . 

J 

Part  B. 


SUBJECTS. 

REPS. 

ARRS. 

SUBJECTS. 

AMOUNT 

RECALLED. 

W . 

5-38 

4-71 

7.88 

3.08 

4- 17 

5- 63 

U . 

5.04 

4.96 

3-75 

u . 

w . 

X . 

X . 

N.  learns  rapidly  and  retains  well;  R.  learns  rapidly  and 
retains  moderately.  H.  is  just  the  converse:  he  learns  moder¬ 
ately,  being  a  tie  for  third  place,  and  retains  well.  G.  learns 
moderately  but  does  not  retain  as  well.  J.  gets  some  recom¬ 
pense  for  his  extra  effort,  while  L.  learns  slowly  and  retains 
with  difficulty. 

W.  and  U.  learn  rapidly  and  retain  well,  there  being  very 
little  difference  between  them.  W.  is  the  more  retentive  for 
longer  intervals.  For  a  week — the  interval  of  their  test— 
there  is  no  difference  between  them,  but  W.  retained  series  for 
weeks  after  U.  had  forgotten  them.  X.  learns  slowly  and  has 
difficulty  in  retaining. 

Temperamental  differences  also  come  out  in  the  willingness 
to  take  a  chance.  This  is  shown  by  the  number  of  arrange¬ 
ments.  N.  and  G.  were  speculative.  They  frequently  termi¬ 
nated  the  exposure  of  the  series  before  they  had  learned  them 
sufficiently.  These  were  the  subjects  who  had  on  occasion  to 
take  five  days  to  learn  the  series  instead  of  the  usual  three. 
L.  and  J.  are  cautious.  When  they  end  the  exposure  it  is  safe 
to  say  they  have  the  series  for  that  day,  and  quite  probable 
that  they  will  have  it  the  next  day  without  re-exposure. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY.  65 
VII.  EXPERIMENTS  TO  DETERMINE  THE  VALUE  OF  ARRANGING^ 

After  all  of  the  foregoing  experiments  had  been  completed, 
12  series  were  given  to  the  subjects,  G.,  H.,  J.,  L.,  N.  and  R. 
There  were  four  series  each  of  colors,  sizes  and  forms.  Two 
of  each  were  learned  in  three  successive  days  all  six  being  begun 
on  the  same  day.  The  other  six  were  given  the  next  week. 
In  one  of  the  two  color  series  of  the  first  week  arranging  was 
required  as  in  all  the  foregoing  experiments,  in  the  other  it 
was  omitted  till  the  final  test.  The  same  is  true  of  the  two 
series  of  sizes,  and  the  two  forms  learned  the  first  week.  The 
times  of  exposure  were  the  same  for  every  correlative  pair, 
the  one  with  and  the  one  without  arranging.  During  the 
first  week  the  series  with  arranging  preceded  their  mates  to 
allow  the  subject  to  determine  the  length  of  the  learning  periods. 
However,  to  prevent  the  series  without  arranging  from  being 
at  a  disadvantage  from  too  short  exposure,  certain  extra  expo¬ 
sures  were  given  by  the  operator  on  the  third  day.  To  be 

‘  This  question  is  very  important  wherever  it  is  desired  to  study  the  learning 
process  as  well  as  the  recall.  For  in  order  to  ascertain  the  learner’s  progress 
towards  complete  temporary  mastery  of  the  material  it  is  necessary  to  test  him 
from  time  to  time.  This  gives  two  different  measures,  learning  time  and  testing 
time  or  number  of  tests.  The  attempt  to  reproduce  a  material  nearly  always 
aids  in  memorizing  it.  Ebbinghaus  assumed  that  a  test  or  attempt  to  repeat 
a  series  is  equivalent  to  a  presentation  of  it,  but  this  is  clearly  unsatisfactory. 
Stephan  Witasek  has  made  an  exhaustive  study  of  the  relative  efficiency  of  read¬ 
ings  and  attempts  at  recital  in  bringing  series  of  nonsense  syllables  up  to  perfect 
memorization,  and  in  producing  recall  after  an  hour.  (Ueber  Lesen  und 
Rezitieren  in  ihren  Beziehungen  zum  Gedachtnis.  Ztsch.  f.  Psych.,  44:  161-85 
and  246-82.)  He  found  that  for  immediate  recall  6  readings  and  5  recita¬ 
tions  enabled  the  persons  to  recite  the  series  in  one  half  the  time  required  by 
II  readings  alone,  and  required  only  one  thirteenth  as  many  promptings. 
(The  Ebbinghaus  prompting  method  is  the  one  referred  to.)  The  superiority 
of  the  recitation  in  producing  recall  after  an  hour  is  not  as  marked  as  in  immed¬ 
iate  recall.  Thus  various  mixtures  of  readings  and  recitations,  the  readings  of 
course  always  preceding,  compared  with  an  equal  number  of  readings  alone, 
effected  an  average  saving  of  about  il  per  cent  in  time  and  16  per  cent  in 
promptings  in  the  final  test.  The  foregoing  disregards  time  consumed  by  the 
two  methods.  A  recitation  aided  by  promptings  takes  more  time  than  a  reading. 
However,  the  author  shows  that  even  on  a  time  basis  a  combination  of  readings 
and  recitations  is  more  economical  than  readings  alone.  From  any  point  of 
view  recitations  are  far  superior  to  readings  in  impressing  value.  The  signifi¬ 
cance  of this  result  for  pedagogy,  for  determining  the  best  methods  of  study,  is 
worth  noting. 


66 


HARVEY  ANDREW  PETERSON. 


more  explicit,  on  the  first  day  the  subject  wholly  determined 
the  time.  He  took  as  much  as  he  thought  would  enable  him 
to  arrange  the  first  series  of  each  pair  correctly  the  next  day, 
and  the  operator  allowed  him  the  same  time  on  the  second 
series  of  each  pair.  On  the  second  day  the  procedure  was  the 
same  if  he  did  not  have  them  correctly  in  the  preliminary  test 
of  that  day.  If  he  did  have  them  correctly,  he  was  given  a 
7-second  exposure  of  both  series  of  the  pair.  The  procedure 
was  repeated  on  the  third  and  last  day,  for  sizes  and  colors, 
but  forms  were  dropped  after  the  second  day,  because  they 
would  have  been  over-learned  by  continuance.  The  aim  of 
these  conditions  was  to  bring  the  series  approximately  up  to 
our  previous  standard,  perfect  retention  for  a  day.  However, 
since  having  arranged  a  series  was  equivalent  to  seeing  it 
again,  and  since  it  was  desirable  for  exactness  to  spread  the 
learning  time  of  both  types  of  series  over  the  same  number 
of  days,  it- was  necessary  to  give  a  brief  exposure  of  both  series 
(the  one  with  and  the  one  without  arranging)  whenever  one 
was  seen.  This  was  the  purpose  of  the  7-second  exposures. 
Hence  our  procedure  was  slightly  different  from  the  one  used 
in  the  past.  In  the  second  week  the  operator  wholly  deter¬ 
mined  the  length  of  the  learning  times,  and  made  them  the 
same  as  the  series  of  the  first  week  for  that  subject.  The 
series  without  arranging  now  preceded  its  mate.  Finally, 
there  was  a  reversal  within  the  pairs.  The  series  in  connection 
with  which  three  of  the  subjects  arranged  were  the  ones  with 
which  the  other  three  subjects  did  not  arrange.  The  purpose 
of  this  reversal  was  to  test  the  assumed  equality  in  difficulty 
of  the  correlative  series.  The  results  substantiated  the  assump¬ 
tion  in  the  main. 

All  the  other  conditions  were  the  same  as  in  the  simultaneous 
series  of  V  2.  The  subject  was  required  to  associate  the  terms 
with  their  spatial  positions.  The  series  were  displayed  on 
cardboard  sheets,  14  X  22  inches,  the  arrangement  being  in 
three  vertical  columns  of  two  terms  each,  except  the  middle 
column,  which  had  three.  The  usual  expedients  to  minimize 
interference,  in  particular,  individual  series-shape  and  series- 
color,  were  used.  The  final  test  of  the  first  six  series  occurred 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  67 

in  the  midst  of  learning  the  second  six  in  order  to  retain  the 
normal  interference  factor,  constantly  operative  in  our  past 
work. 

The  procedure  with  the  three  successive  subjects  U.,  W.  and 
X.  was  similar.  The  consonants  G,  H,  N,  P,  Q,  W  and  Y 
were  associated  with  I2  series,  4  each  of  colors,  sizes  and  forms. 
Three  of  the  letters  were  white,  the  rest  black.  The  learning 
conditions  were  modeled  after  those  described  above,  while 
the  testing  conditions  were  the  same  as  in  the  regular  work  of 
these  subjects. 

For  the  six  simultaneous  subjects  the  value  of  an  arrange¬ 
ment  was  determined  by  dividing  the  total  number  of  seconds 
spent  in  learning  the  six  series  in  which  there  virs  no  arranging 
by  the  number  of  terms  recalled  in  those  series  after  a  week, 
and  then  dividing  the  difference  between  the  total  recall  in 
the  six  series  with  arranging  and  the  six  without,  by  the  total 
number  of  arrangements  used.  The  first  operation  gave  the 
number  of  seconds  of  learning  time  that  would  produce  one 
term  in  recall  with  this  subject,  while  the  second  operation 
gave  the  number  of  arrangements,  or  the  fraction  of  an  arrange¬ 
ment,  that  would  produce  one  term  in  recall.  These  two 
quantities  were  therefore  equivalent.  Precisely  the  same 
method  was  pursued  in  calculating  the  value  of  an  arrange¬ 
ment  for  the  successive  subjects,  except  that  the  learning  times 
were  given  in  repetitions  instead  of  minutes  and  seconds.  The 
values  thus  obtained  for  the  different  subjects  were  as  follows: 


Value  of  an  Arrangement. 


SUBJECT. 

SUBJECT. 

SUBJECT. 

G . 

5  secs. 

12.35 

21 .8  secs 

L . 

10  secs. 

12.35  ®^cs. 
10  secs. 

U . 

1 .673  reps, 
nothing 
2.617  reps. 

H . 

N . 

w . 

T . 

R . 

X . . . . 

J 

For  the  two  subjects  who  were  dropped  from  the  experiment 
after  the  series  of  grays  and  violets,  McP.  and  F.,  10  secs,  was 
taken  as  the  value. 


68 


HARVET  ANDREW  PETERSON. 


VIII.  CONCLUSION. 

In  summing  up  the  results  of  the  investigation,  it  is  well  to 
call  attention  to  the  fact  that  it  is  not  primarily  an  inquiry 
into  the  effects  of  novelty  on  memory.  Had  this  been  the  aim 
the  same  typographical  variations  would  not  have  been  used 
for  eight  consecutive  weeks,  nor  the  same  variations  in  plane 
areas  for  over  four  months.  The  experiments  rather  contrast 
the  effects  of  simplicity  with  dissimilar  complexity,  when  a 
few  types  of  each  are  used  a  long  time. 

Language,  spoken  and  written,  is  full  of  symbols  relatively 
simple  and  similar.  The  sameness  of  a  page  of  print  contrasted 
with  the  variety  afforded  to  the  eye  by  looking  at  natural  objects 
is  striking.  The  possibilities,  however,  of  improving  the 
memory  for  language,  by  introducing  mechanical  variations, 
as  suggested  to  us  by  the  experiments  of  Dr.  Gordon,  have 
proved  to  be  decidedly  limited.  In  the  absence  of  variation  in 
meaning,  as  is  the  case  with  nonsense  syllables  for  example, 
the  memory  is  permanently  improved  by  the  addition  of  a  few 
variations,  particularly  position  and  size,  but  if  the  number 
of  variations  be  increased  considerably,  say  to  three  or  four, 
distraction  enters,  there  is  no  further  improvement  and  there 
may  be  a  loss.  That  such  variations  are  of  great  aid  in  arrest¬ 
ing  the  attention,  when  they  have  the  feature  of  novelty,  is  a 
popular  conviction  which  experiment  would  doubtless  verify. 
If,  however,  the  variation  takes  the  form  of  experiencing  fewer 
of  one  thing  than  of  another,  the  memory  for  the  few  is  cer¬ 
tainly  better  than  the  memory  for  the  many,  as  proved  by  the 
experiments  of  Prof.  Calkins. 

But  language  differs  from  nonsense  syllables  in  having  mean¬ 
ing,  in  itself  a  powerful  variation,  and  the  experimental  results 
give  no  basis  for  the  belief  that  the  memory  for  language  is 
permanently  better,  when  the  words  vary  in  mechanical  ways. 
Our  own  experiments  were  few  in  number,  but  convincing. 
When  the  attempt  is  made  to  vary  the  meaning,  a  difficulty  in 
technique  arises,  which  is  by  no  means  a  small  one,  namely, 
the  difficulty  of  keeping  the  simpler  material  simple  and  dis¬ 
connected.  Even  single  adjectives  or  two-place  numbers  sug- 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  69 


gest  acquired  connotations  so  readily  that  the  material  rapidly 
becomes  complex,  and  has  the  advantage  over  the  material 
called  complex  that  it  is  already  made  up  of  units.  This  was 
the  case  with  our  experiments  with  words  and  sentences,  and 
numbers  and  biographical  facts.  However,  the  results  at  least 
show  that  when  the  learning  time  is  fixed  and  sufficient  for 
comprehending  the  meaning  of  both,  short  sentences  can  be  as 
well  remembered  as  single  words.  All  three  of  our  language 
experiments  showed  conclusively  that  a  person  will  seek  differ¬ 
entials  among  the  things  to  be  associated,  but  will  give  the 
preference  to  ones  already  connected  in  his  experience,  if  they 
can  be  found. 

We  pass  next  to  the  experiments  with  plane  areas.  We 
found  that  forms  were  far  more  associable  than  colors  and 
sizes,  that  is  to  say,  the  associations  were  much  more  quickly 
established  between  forms  and  something  else  than  between 
colors  or  sizes  and  something  else.  In  this  result  all  nine  sub¬ 
jects  agree.  We  know  of  no  other  experiments  on  this  subject 
except  those  of  Bigham.^  He  found  that  colors  were  slightly 
more  associable  than  forms  in  immediate  recall,  but  after  2 
hours  and  24  hours  the  result  was  the  reverse  by  larger  differ¬ 
ences  than  before.  The  res  onse  times  in  immediate  recall 
of  forms  were  also  longer  than  in  the  case  of  colors.  His 
method  was  similar  to  ours  in  the  use  of  duplicate  series  for 
testing,  but  differed  in  the  very  important  respect  that  the 
same  ten  forms  and  ten  colors  were  used  over  again  in  every 
series.  The  test  was  association  with  position  as  in  our  experi¬ 
ment.  The  re-use  of  the  same  forms  would  under  these 
circumstances  produce  interference,  the  greater  for  forms 
because  of  their  more  ready  associability.  The  better  recall 
of  forms  after  two  and  after  twenty-four  hours,  that  is  the 
fact  of  reversal,  cannot  be  understood  without  knowing  how 
many  series  of  a  kind  were  given. 

The  relative  associability  of  sizes  and  colors  differs  in  our 
results  with  different  subjects,  with  the  balance  in  favor  of 
colors.  Four  persons  remember  colors  better;  two,  sizes;  and 


^  Bigham,  John:  Memory.  Psych.  Rev.,  1894,  I,  453. 


70 


HARVET  ANDREW  PETERSON. 


two  show  no  marked  difference.  The  ninth  subject  is  dis¬ 
regarded  because  of  low  recall.  However,  if  the  slighter  differ¬ 
ences  shown  by  two  persons  classed  as  equal  be  counted,  six 
remember  colors  better  than  sizes,  while  two  are  the  opposite, 
and  by  very  large  amounts  in  both  cases. 

The  very  great  superiority  of  forms  over  colors  and  sizes  is 
certainly  due  to  the  far  greater  variety  within  a  limited  space 
which  the  realm  of  forms  offers.  Had  all  the  form-varying 
series,  instead  of  one-half,  consisted  solely  of  forms  used  only 
once,  the  superiority  of  forms  would  have  been  still  greater  by 
a  considerable  amount.  Yet  as  many  forms  as  that  could 
easily  have  been  found  without  making  the  similarity  great.  The 
simple  fact  is  that  there  is  a  large  number  of  easily  discrim- 
inable  forms,  while  there  are  only  a  very  few  easily  discriminable 
colors  and  sizes,  so  far  as  the  memory  for  long  intervals  is 
concerned.  On  the  other  hand  the  experiment  does  not  do 
justice  to  the  possibility  of  color.  It  would  be  interesting  to 
know  what  would  be  the  result  of  combining  several  colors  in 
each  term.  The  striking  color  effects  of  practical  life  are 
oftener  color  contrasts  than  single  colors.  While  only  experi¬ 
mentation  can  decide  the  question,  our  own  results  lead  us  to 
expect  only  slight  improvements  for  color  from  this  source. 

While  our  earlier  experiments  were  relevant  to  the  memory 
for  language,  the  later  ones  with  plane  areas  are  like  the  mem¬ 
ory  for  objects,  and  here  our  results  were  much  more  positive 
and  extended.  We  may  disregard  the  differences  between  the 
associations  with  position  and  those  with  numbers,  and  treat 
all  nine  subjects  together.  The  questions  raised  in  the  original 
statement  of  our  problem  may  be  answered  as  follows.  On 
the  low  level  of  variety  represented  by  shades  of  gray  and  shades 
and  tints  of  one  color,  the  advantage  of  additional  variations 
is  great  and  is  manifested  by  all  six  subjects  tried.  By  a  men¬ 
tal  economy  the  additions,  here  more  easily  discriminated  than 
the  grays  and  violets,  become  the  more  prominent,  although  a 
bona  fide  association  is  made  between  them  by  the  time  the 
learning  process  is  complete.  In  most  cases  the  person  could 
tell  which  gray,  or  shade  or  tint  of  violet,  went  with  a  form  or 
size,  if  given  both  variations  to  put  together.  This  process  of 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  7 1 

remembering  a  less  discriminable  thing  by  a  more  discriminable 
associate  is  easily  identified  in  life.  Students  distinguish  their 
notebooks  by  the  fasteners,  marks  of  rough  usage  or  even 
bits  of  color.  Books  are  distinguished  by  their  variation  in 
color,  because  the  shape  is  so  much  less  discriminable.  In 
education  arithmetical  rules  are  clothed  in  striking  examples. 

With  the  passage  to  the  higher  levels  represented  by  different 
colors  and  different  forms,  when  the  variations  added  are  less 
discriminable  than  the  bases,  five  of  the  nine  subjects  no  longer 
profit  by  the  increase  in  complexity.  The  two  other  persons 
in  the  simultaneous  position  associations  and  two  in  the  num¬ 
ber  associations  with  areas  still  profit.  No  limit  was  found  for 
them.  When,  however,  the  variation  added  is  more  discrimin¬ 
able  than  the  base,  all  of  the  subjects  again  profit  by  the  addition. 
This  is  the  case  when  in  our  type  of  series  called  Colored 
Forms  a  form  variation  is  added  to  color.  The  advantage  is 
almost  as  marked  as  on  the  lower  level. 

The  question  why  the  increases  in  complexity  cease  to  be  an 
advantage  is  next  in  order.  The  ability  to  profit  by  these 
increases  is  not  a  function  of  speed  of  learning,  as  would 
naturally  be  expected.  Quickness  in  learning  here  represents 
good  powers  of  discrimination  and  facile  associative  processes. 
The  figures  given  in  Table  8  show  that  of  the  four  persons  who 
profited  longest  by  the  increases  in  complexity,  R.  and  J.,  and 
U.  and  X.,  two  rank  first  and  two  last  in  rapidity  of  learning  the 
series.  The  ranking  is  the  same  if  only  pure  colors,  sizes  and 
forms  are  averaged.  This  restriction  can  be  demanded  with 
some  justice,  because  if  those  who  have  trouble  in  discriminat¬ 
ing  the  terms  are  the  ones  who  profit  longest  by  the  added 
variations,  their  slower  discrimination  would  show  itself  most 
before  the  variations  were  added. 

On  the  other  hand  the  five  to  whom  the  complex  material 
was  not  the  better  are  in  agreement  as  to  the  presence  of  dis¬ 
traction  in  the  complex  series.  While  distraction  is  therefore  the 
most  probable  cause  at  the  present  time,  special  experiments 
on  the  span  of  attention  are  necessary  to  decide  the  matter. 

It  is  now  possible  to  offer  an  explanation  for  some  of  the 
differences  in  the  memory  for  different  materials,  and  the  same 


72 


HARVEY  ANDREW  PETERSON. 


materials  learned  in  different  ways,  which  were  spoken  of  in 
the  beginning.  Objects,  actions  and  pictures  are  better  remem¬ 
bered  than  words,  because  they  are  more  extensive  and  varied 
stimulations.  Both  get  a  certain  amount  of  variation  from  the 
ideational  suggestions  called  forth,  by  the  connotations,  in  other 
words.  It  is  probable  that  the  ideational  supplementation  is 
somewhat  richer  for  words  than  for  objects,  actions  and  pictures. 
But  with  most  persons  imagery  is  feeble  compared  with  sen¬ 
sory  stimulations,  and  we  are  inclined  to  believe  that  the  advan¬ 
tage  which  words  may  enjoy  in  this  respect  is  relatively  slight. 
On  the  other  hand  in  the  extensiveness  and  dissimilarity  of 
sensory  stimulations  a  series  of  words  cannot  compare  with 
a  series  of  objects  or  pictures.  This  is  ludicrously  brought  out 
when  one  attempts  to  handle  type.  We  rest  our  eyes  from 
print  by  looking  at  our  surroundings.  Contrast  the  extent  and 
variety  of  stimulation  obtained  from  looking  at  a  house,  a 
lawn,  a  lamp,  a  knife,  a  piano-player  and  a  moving  train  of 
cars  with  the  smallness  and  similarity  of  the  stimulations 
obtained  by  looking  at  their  printed  words  just  given,  or  even 
printed  and  read  aloud.  Corresponding  to  the  more  exten¬ 
sive  and  varied  original  brain  excitations  of  things  are  the  more 
easily  aroused  and  numerous  mental  cues  in  recall,  and  the 
greater  likelihood  of  freedom  from  the  interference  due  to  sim¬ 
ilarity.  If  the  brain  excitations  obtained  from  seeing  and  hear¬ 
ing  the  series  of  things  mentioned  above  be  denoted  by  the 
letters  ABCD,  DEFG,  GHIJ,  etc.,  those  obtained  from  looking 
at  their  printed  names  and  speaking  them  should  be  represented 
by  the  letters  mnop,  nopq,  opqr,  etc.,  even  after  the  differences 
due  to  suggested  imagery  are  included. 

The  explanation  is  the  same  for  the  fact  that  words  presented 
to  several  senses  are  better  remembered  than  those  presented  to 
one  only.  Whitehead  has  shown  that  when  things  are  learned 
visually,  there  is  a  filtration,  so  to  speak,  through  from  our  visual 
to  our  auditory  experience  taking  place  at  the  time  of  the  visual 
learning,  so  that  if  a  week  later  the  same  thing  be  learned  audi¬ 
torily,  it  takes  but  little  more  time  than  to  relearn  it  visually,  and 
of  course  much  less  time  than  to  learn  a  new  series  auditorilvd 

^Whitehead,  L.  G.:  Psych.  Rev.,  1896,  III,  p.  258. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY.  73 

The  same  thing  is  true  if  the  first  learning  is  auditory  and  the 
second  visual.  Here  as  in  our  own  experiments  the  connecting 
process  goes  on  during  learning,  but  in  this  case  the  connec¬ 
tion  is  with  images  instead  of  other  perceptions.  The  same 
process  takes  place  in  learning  through  several  sense  organs  at 
once.  If  we  not  only  see  but  pronounce,  We  get  a  more  varied 
stimulation  than  if  we  merely  see  the  words,  and  if  we  read 
them  aloud  the  stimulations  are  still  more  varied  compared 
with  the  visual  alone,  and  the  liability  to  confusion  in  recall 
is  correspondingly  less,  just  on  account  of  this  growing  varia¬ 
tion.  Doubtless  the  well-known  summation  effects  of  a  number 
of  weak  stimuli  are  also  responsible  for  the  difference.  We 
seem  to  get  the  meaning  more  completely  when  we  read  a  page 
aloud  than  when  we  read  it  to  ourselves.  This  indicates  that 
the  visual,  auditory  and  enunciatory  stimulations  combined 
are  more  effective  than  one  or  two  alone  in  arousing  associa¬ 
tions  of  an  ideational  type.  Furthermore,  it  is  not  to  be  for¬ 
gotten  that  we  are  dealing  here,  in  the  case  of  language  at  least, 
with  complexes  that  are  already  apperceptive  units,  owing  to 
early  schooling.  The  case  is  somewhat  different  from  that 
of  our  own  experiment,  where  the  combinations  were  con¬ 
stantly  new. 

One  of  the  original  and  less  common  features  of  this  inves¬ 
tigation  is  the  length  of  the  interval  before  the  memory  is 
tested.  There  are  few  extended  investigations  of  the  memory 
for  materials  after  intervals  as  long  as  one  and  two  weeks. 

Finally,  to  the  technique  of  memory  work  we  offer  a  contri¬ 
bution.  The  method  of  measuring  the  memory  for  different 
materials  by  the  amount  of  time  or  repetitions  required  to 
bring  them  up  to  the  same  level  of  efficiency  meets  with  the 
difficulty  of  evaluating  the  tests  taken  to  determine  progressive 
efficiency.  We  propose  a  solution  of  this  difficulty,  namely,  a 
separate  determination  for  each  person,  of  the  average  worth 
of  a  test  in  terms  of  learning  time  or  repetitions,  the  two  meas¬ 
urements  to  be  rendered  equivalent  through  what  each  will 
produce  in  recall. 


74 


HARVET  ANDREW  PETERSON. 


IX  APPENDIX. 

1.  Plates. 

The  following  plates  give  the  shapes  and  relative  sizes  of  the  form-varying 
series.  The  actual  dimensions  and  the  colors  employed  are  given  in  the 
‘Description  of  Series’  on  the  pages  immediately  succeeding. 

With  three  subjects  U,  W,  and  X,  certain  forms,  here  called  ‘Substituted 
Forms,’  replaced  some  of  those  in  the  regular  series  in  order  to  eliminate  repe¬ 
tition.  They  are  numbered  to  correspond  with  the  figures  which  they  replaced, 
and  the  distinctive  letter  B  is  added.  The  first  three  forms,  iB,  4B,  and  5  B 
belong  to  Forms  I;  the  fourth,  7B,  belongs  to  Forms  II;  and  the  last  two  in 
the  row,  iB  and  6B,  belong  to  Forms  B.  In  the  next  row  iB,  zB,  and  7B 
belong  to  C.  F.  d.  S.  Ill,  and  the  remaining  five  belong  to  C.  F.  d.  S.  IV. 

2.  Description  of  Series  used  in  V  2  and  5. 

Colors.  Each  term  contained  50  sq.  cm. 

Series  I.  Eight-point  stars.  Yellow  orange  t.  2,  green,  cool  gray  no.  i 
blue  sh.  2,  A-yellow  medium,  green  yellow  t.  2,  red  orange  sh.  i. 

Series  II.  Squares.  Orange  red  t.  2,  yellow  orange  sh.  2,A-blue  green  dark, 
yellow,  red,  green  t.  l,  A-red  light. 

Series  III.  Oblongs.  Orange  yellow  t.  i,  red  violet  sh.  2,  orange  red  t.  i, 
blue  green  sh.  i  green  yellow  t.  i,  A-green  yellow  dark,  A-green  light. 

Series  IV.  Round-cornered  squares.  Black,  violet  red  t.  2,  orange  red  sh. 
2,  cool  gray  no.  2,  green  sh.  2,  A-yellow  orange  medium,  green  blue  sh.  1. 

Sizes.  Series  i.  Red  oblongs,  height  twice  the  width.  Irregular  ratio  of 
terms  as  follows:  i  :  2  =  4,  2  :  3  =  3.06,  3:4  =  1.24,  4  :  5  =  1.5,  5  :  6  =  1.4, 
6  :7  =  1.5. 

Series  II.  Equilateral  triangles.  A-yellow  orange  dark.  Geom.  ratio, 2.77, 
beginning  with  an  area  of  .5  sq.  cm.  for  the  smallest. 

Series  III.  Circles.  Blue  violet  sh.  2.  Geom.  ratio,  2.77.  Smallest  term, 
.5  sq.  cm. 

Series  IV.  Truncated  cones,  sides  inclined  one-tenth  the  width  of  the  base 
on  each  side.  Yellow  orange,  and  irregular  ratio  of  terms  as  follows:  1:2  = 
3.9,  2:  3  =  4.1,  3:4  =  2.98,  4:5  =  1.69,  5  :  6  =  2.1,  6  :  7  =  1.9. 

The  order  in  which  the  sizes  were  placed  in  any  series  was  determined  by 
chance  as  in  the  gray  and  violet  sets,  excluding  the  cases  there  excluded. 
The  arrangements  employed  in  the  above  series  were  the  following,  reading  the 
series  from  left  to  right.  The  figures  give  the  areas  in  sq.  cm. 

Series  I.  40.5  60.5  2  8  84.5  128  24.5. 

Series  II.  (i  is  the  smallest)  1625347. 

Series  III.  2451376. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITT  ON  MEMORY.  75 


76 


HARVET  ANDREW  PETERSON. 


INFLUENCE  OF  COMPLEXITF  AND  DISSIMILARITT  ON  MEMORT.  77 


COLORED  FORMS  OF  DIFFERENT  SIZES. 

I 


n 


78 


HARVET  ANDREW  PETERSON. 


Series  IV.  1.95  .50  40.6  162.2  24  8.05  84. 

It  will  be  noted  that  the  aggregate  area  of  each  series  was  350  sq.  cm. 


Colored  Sizes.  These  series  are  the  simplest  advance  in  complexity.  As  the 
name  indicates  they  vary  in  area  and  color.  To  render  them  comparable  with 
series  varying  in  size  only,  the  term-areas  of  Series  I  repeat  those  of  Sizes  I, 
Series  II,  of  Sizes  IV,  Series  III  and  IV,  of  Sizes  II  and  III.  The  series-shapes 
were  however  new.  The  order  of  occurrence  of  the  terms  may  be  represented 
as  follows,  the  topmost  one  being  on  the  left  end.  The  figures  again  indicate 
the  sizes,  i  representing  the  smallest,  2  the  next  smallest,  etc.  The  combination 
of  color  with  size  was  determined  by  chance  after  the  seven  colors  for  the  series 
had  once  been  selected.  However  very  small  terms  were  not  given  very  light 
colors. 


Senes  I . 

2  yellow  green 

3  yellow  orange  dark 
I  red  sh.  2 

7  orange  yellow  t.  i 

6  red  orange 

4  blue  green  sh.  2 

5  violet  t.  I. 

Series  III. 

3  A-green  medium 

4  blue  t.  I 

7  A-orange  red  dark 

5  green  yellow  t.  2 

1  black 

6  A-orange  light 

2  A-red  violet  dark 


Senes  II. 

2  blue 

I  orange  red 

5  orange  sh.  i 

7  yellow  orange  t.  i 

4  green  yellow 

3  blue  t.  2 

6  red  violet  t.  i. 

Series  IV. 

3  violet 

1  A-green  yellow  dark 

6  blue  green  sh.  i 

2  A-yellow  orange  light 

5  green  blue  t.  2 

4  red  orange  sh.  2 

7  yellow  t.  2 


Forms.  (See  plates.) 

Colored  Forms.  These  series  also  varied  in  two  ways,  color  and  form.  The 
forms  are  given  in  the  plates.  Each  term  contained  50  sq.  cm.  The  colors 
in  order  from  left  to  right  in  the  series  were  as  follows: 

Series  I.  Fig.  i  yellow.  Fig.  2  A-green  medium.  Fig.  3  red  violet  t.  i.  Fig. 
4  yellow  green.  Fig.  5  black.  Fig.  6  A-orange  red  medium.  Fig.  7  orange  t.  2. 

Series  II.  Fig.  i  green.  Fig.  2  orange.  Fig.  3  orange  yellow  sh.  l.  Fig.  4 
red.  Fig.  5  green  t.  2,  Fig.  6  yellow  orange  sh.  2,  Fig.  7  violet. 

Series  III.  Fig.  i  A-yellow  orange  dark.  Fig.  2  blue  sh.  2,  Fig.  3  red  t.  i. 
Fig.  4  yellow  green.  Fig.  5  orange  yellow  t.  i.  Fig.  6  red  violet  sh.  i.  Fig.  7  yel¬ 
low  green  sh.  2. 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  79 


Series  IV.  Fig.  i  warm  gray  no.  i,  Fig.  2  orange  yellow  t.  2,  Fig.  3  green 
yellow  t.  I,  Fig.  4  blue  t.  i,  Fig.  5  A-orange  red,  Fig.  6  violet  red,  Fig.  7  A-yel- 
low  orange  medium. 


Colored  Forms  of  Different  Sizes.  These  series  varied  in  three  ways  and 
represented  the  maximum  number  of  variations  which  were  combined  in  a  single 
series.  The  variations  were  in  color,  size  and  form.  The  forms  are  given  in 
the  plates,  the  sizes  and  colors,  here.  The  ratios  existing  between  each  two 
successive  terms  in  series  I  and  II  were  the  same  as  in  Sizes  I,  and  the  actual 
areas  were  also  the  same  as  there.  In  series  III  and  IV  the  ratios  were 
I  :  2  =  4,  2  :  3  =  2.25,  3  :  4  =  2,  4  :  5  =  2.17,  5  :  6  =  2.6,  6:7  =  3.25. 

1:2  =  2.5,  2:3=  2.5,  3  :  4  =  2,  4  :  5  =  2.5,  5:6  =  2.17,  6:7  =  1.35. 


Fig.  I 
“  2 


<( 

« 

{( 

(( 

<( 


3 

4 

5 

6 

7 


Fig.  I 


a 


2 


a 

<( 

u 

u 

(( 


3 

4 

5 

6 

7 


Fig.  I 


u 


2 


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(( 

(( 

(( 

(( 


3 

4 

5 

6 

7 


Fig.  I 


(t 


2 


<( 

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H 

U 


3 

4 

5 

6 

7 


8. 

84.5 

40.5 

128. 

2. 

24-5 

60.5 


sq.  cm 

u 

u 

a 

u 

u 

(( 


60.5 
24-5 

128. 

2. 

84-5 

40.5 

8. 


sq.  cm 

u 

n 

u 

u 

u 

u 


19.2 

162. 

4-5 

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50. 

2. 

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sq.  cm 

U 

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43.75  sq.  cm 
128 . 


17 

3 

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5 

5 

75 

4 


95 


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u 


u 

u 

a 


Series  I. 


Series  II. 


Senes  III. 


Senes  IV. 


A-yellow  orange  dark 
violet  red 
A-yellow  light 
yellow 
A-blue  dark 
yellow  green  sh.  2 
blue 


green  t.  i 

orange  yellow  sh.  I 
warm  gray  no.  2 
orange  red 
green  blue  sh.  i 
orange 
A-red  light 


black 

violet 

orange  yellow  sh.  i 
red  violet  t.  2 
yellow  green  sh.  2 
red  t.  2 
blue  t.  I 


blue  violet 
green  blue  sh.  i 
violet  red 
warm  gray  no.  2 
green  yellow  sh.  2 
red  sh.  2 
A-yellow  light 


8o 


HARVET  ANDREW  PETERSON. 


Each  of  the  first  two  series  aggregates  348  sq.  cm.,  the  third  247  and  the 
fourth  298  sq.  cm. 

Extra  Series.  Colors  A.  Blue  sh.  2,  yellow  orange  sh.  2,  violet,  orange, 
green,  A-violet  blue  light,  red.  Oblongs,  height  twice  the  width. 

Colors  B.  A-yellow  light,  red  violet  t.  2,  red  t.  l,  yellow,  warm  gray  no.  2, 
blue  green,  yellow  green  t.  l.  Same  series-shape  as  in  the  preceding  one. 

Sizes  A.  Isosceles  triangles,  height  twice  the  base.  Blue  t.  2,  geom.  ratio 
of  2.5  beginning  with  an  area  of  .5  sq.  cm.  for  the  smallest  term.  Total  area 
of  series,  204  sq.  cm.  Order:  5416372. 

Sizes  B.  Truncated  Cones,  A-yellow  dark  in  color.  The  ratios  were  1:2  = 
4.5,  2:3=  2.78,  3:4  =  2.6,  4:5=  2.03,  5:6  =  1.3,  6:7  =  1.92.  The 
actual  areas  in  order  from  left  to  right  were,  in  sq.  cm.:  25  64  2  169  9 

324  130.  The  total  area  was  723  sq.  cm. 

Sizes  C.  Quadrilaterals  formed  by  superposing  upon  a  square  a  right 
triangle  of  the  same  dimensions  with  hypotenuse  to  the  left.  Green  sh.  2  in 
color.  The  ratios  were,  4,  4,  3,  3.5,  1.93,  1.58.  The  actual  areas  in  their 
order  were  in  sq  cm.:  2  162  24  84  256  .5  8.  The  total  area  was  536.5 

sq.  cm. 

In  the  next  two  series  the  areas  of  Sizes  I  were  used. 


Colored  Sizes  A. 

4  blue  green 

2  red  orange  t.  2 

7  warm  gray  no.  l 

5  green  t.  2 

I  red  orange 

3  blue  t.  I 

6  A-green  yellow  medium 


Colored  Sizes  B. 

5  orange  red  sh.  i 

2  green  sh.  2 

4  orange  yellow  t.  i 

3  red  t.  2 

7  cool  gray  no.  i 
I  A-yellow  orange  dark 

6  blue 


Forms  A  and  B.  These  are  sufficiently  described  in  the  plates.  The  results 
obtained  from  them  were  not  used  in  the  tables,  because  the  forms  in  them 
had  been  used  once  before,  and  there  was  already  a  sufficiency  of  such  series. 


3.  Analysis  of  Errors  in  V  2. 

In  the  pages  immediately  following  the  errors  of  Tables  4  and  5  will  be 
analyzed.  The  results  of  two  subjects  will  be  treated  in  detail  including  every 
series,  every  error  in  the  final  test  and  some  of  the  errors  made  in  learning. 
Some  of  the  explanations  are  conjectural,  and  of  questionable  worth;  many 
others  are  beyond  question  the  true  causes  of  the  errors.  The  account  is  to 
a  very  large  extent  a  story  of  interference  due  to  similarity.  It  will  be  recalled 
that  introspections  were  not  allowed  before  the  final  test,  so  that  when  they 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  8l 


were  given,  most  of  them  were  not  of  value.  The  conclusions  given  below  are 
therefore  mainly  the  result  of  a  study  of  the  arrangements  of  duplicate  series 
handed  in  by  the  subject.  Where  introspections  were  used  it  is  made  evident  in 
the  text.  The  extra  series  denoted  by  the  letters  A,  B,  etc.,  are  included.  It 
is  essential  to  remember  that  in  the  interval  of  13  days  between  the  learning 
and  the  testing  of  a  series  two  more  rounds  of  similar  series  were  learned. 
When  the  particular  test  is  not  mentioned  it  is  always  the  final  one  that  is 
meant.  By  ‘wing’  is  meant  the  three  terms  on  either  side  of  the  middle  term.^ 

Subject  R. 

Col.  Sizes  I  and  II,  and  Cols.  A.  In  learning  Col.  Sizes  I  the  only  error 
was  an  exchange  of  3  yellow  orange  and  4  blue  green  belonging  in  2d 
and  6th  places  respectively.  The  error  was  probably  due  to  their  similarity 
in  size.  It  occurred  three  times  on  successive  days.  When  the  next  week  Col. 
Sizes  II  was  learned  the  influence  of  I  was  shown  in  erroneously  moving  green 
yellow  from  5th  to  ist  place  where  a  yellow  green  had  stood  the  previous  week. 
The  error  occurred  twice,  with  no  others.  When  in  the  third  week  Col.  Sizes 
I  received  its  final  test,  aside  from  an  exchange  of  two  small  adjacents,  3  yellow 
orange  and  i  red,  the  only  error  was  a  removal  of  yellow  to  5th  place.  Here 
the  corrections  which  the  subject  got  in  II  worked  to  the  undoing  of  I.  When 
the  following  week  II  is  tested  the  only  error  is  moving  green  yellow  to  the  left 
end,  this  time  to  second  place  instead  of  to  first.  The  original  error  has  recurred. 
Cols.  A,  which  was  learned  with  Col.  Sizes  I,  shows  the  influence  of  this  strug¬ 
gle.  Its  yellow  orange  is  moved  from  2d  to  7th  place,  its  green  from  5th  to 
3d  place.  This  is  very  much  like  the  first-mentioned  error  in  Col.  Sizes  I. 
The  only  other  errors  were  an  exchange  of  adjacents,  violet  blue  and  red. 

C.  F.  d.  S.  III.  Exchange  of  adjacent  terms  in  final  test,  one  pair  only. 

Forms  I.  In  the  final  test  aside  from  one  exchange  of  adjacents,  the  errors 
are  caused  by  moving  Fig.  7  to  3d  place.  No  explanation  ascertainable. 

Sizes  B  and  C.  The  kind  of  schemes  or  systems  most  frequently  made  use 
of  by  all  the  subjects  when  the  exposure  was  simultaneous  is  well  illustrated 
by  the  one  us'id  by  R  in  Sizes  B.  The  correct  order  was  3416275,  i  repre¬ 
senting  the  smallest,  2  the  next  smallest  term,  etc.  Her  system  according  to 
her  own  testimony  was  an  ascending  ‘sky-line’  from  ist  to  6th  places,  3467, 
the  smallest  and  next  smallest  forming  a  second  ascending  series  interpolated 
in  the  first  at  the  3d  and  5th  positions.  The  last  term  stood  apart.  In  the 
final  test  the  general  nature  of  the  scheme  remains,  but  the  details  have  become 

^  To  understand  these  analyses  of  errors  the  Description  of  Series  on  pp. 
74-80  doubtless  will  have  to  be  frequently  consulted.  The  prefixed  figures  2, 
3,  etc.,  mean  the  second  size,  third  size,  etc,  counting  from  the  smallest. 


82 


HARVEY  ANDREW  PETERSON. 


confused,  as  shown  by  her  arrangement  3451726.  The  next  week,  when  Sizes 
C  came  up  for  final  test  the  system  which  the  subject  had  employed  in  learning 
B  was  introduced  into  C  with  entire  correctness.  The  subject  is  of  course 
unaware  that  it  had  belonged  to  another  series.  This  is  only  one  of  the  many 
striking  illustrations  in  our  experiment  of  the  law  discovered  by  Muller  and 
Pilzecker,  that  of  two  similar  and  mutually  interfering  associations  the  earlier 
formed  one  becomes  relatively  stronger,  the  greater  the  lapse  of  time  since  the 
later  one  was  learned.^  In  our  own  illustration  the  system  used  in  B  was  imper¬ 
fectly  remembered  when  still  in  the  shadow  of  learning  C,  but  after  the  effects 
of  learning  C  had  had  a  week  to  die  down,  the  B  system  recovered,  unfortu¬ 
nately  for  the  subject,  in  the  wrong  series. 

Forms  II.  This  series  has  three  tall  figures,  distributed  near  the  middle 
and  on  or  near  the  ends.  In  learning,  the  series  was  balanced  about  them  and 
on  one  occasion  Fig.  5  was  put  in  the  middle  place.  After  two  weeks  the  sub¬ 
ject  has  forgotten  the  exceptions  to  the  balanced  scheme,  as  shown  by  her 
arrangement,  in  which  the  three  tall  figures  of  the  series  are  placed  at  the  ends 
and  in  the  middle.  Fig.  2  is  on  the  left,  5  in  the  middle  and  7  on  the  right 
end.  The  low  intermediate  figures  are  not  well  remembered. 

C.  F.  d.  S.  IV.  Figs.  5  and  6  are  exchanged.  Possibly  their  similarity  in 
size  was  a  partial  cause.  The  other  error  was  moving  Fig.  i  to  the  right  of 
Fig.  7,  of  which  no  explanation  other  than  simply  memory-fading  is  offered. 
Both  errors  in  the  final  test  onlv 

j 

Cols.  II.  Many  errors  in  final  test.  No  explanation. 

Cols.  I.  Final  test.  Again  the  arrangement  is  chaotic.  Bright  colors  (red 
and  green)  are  erroneously  put  in  the  middle  where  they  were  in  the  three  other 
color  series  previously  learned. 

Col.  Sizes  A.  The  final  test  is  badly  mixed.  The  subject  places  only  one 
term  correctly, — 2  red  orange.  4  blue  green  and  3  blue  are  exchanged.  They 
are  next  to  each  other  in  size  and  similar  in  color. 

C.  F.  d.  S.  I.  A  single  exchange  of  adjacents.  Figs.  2  and  3. 

C.  F.  d.  S.  II.  Two  exchanges  of  adjacents.  Figs.  2  and  3,  and  4  and  5. 
Shows  interference  of  other  series:  Fig  6  (window)*  is  put  in  ist  place,  occupied 
in  C.  F.  d.  S.  Ill  (which  preceded  the  present  series  with  this  subject)  by  a  figure 
of  the  same  shape,  but  different  color  and  size.  Fig.  i  (slender  vase)  is  put  in 
6th  place  as  in  Forms  B,  seen  r  day  before. 

Col.  Sizes  B.  Three  errors.  Ends,  blue  and  orange  red,  are  exchanged, 
due,  the  subject  says,  to  Cols.  A,  where  a  similar  blue  and  red  were  on  the  ends. 
Latter  series  not  seen  for  30  days.  Orange  yellow  moved  to  the  right  of  the 
term  belonging  in  6th  place.  Reason  not  known. 

'  Muller  and  Pilzecker.:  Ztsch.  f.  Psych.,  Erganzungsbd.  r,  pp.  124  and  138. 

’  These  names  are  inventions  of  the  operator. 


INFLUENCE  OF  C0MPLEXIT2-  AND  DISSIMILARITY  ON  MEMORY.  83 

Cols.  B.  Exchange  of  the  two  terms  considered  colorless  or  ‘dead’  by  the 
subject,  A-yellow  light  and  warm  gray  no.  2. 

Col.  Forms  I.  All  correct. 

Forms  B.  An  exchange  of  two  figures  adjacent  and  relatively  very  similar 
in  shape,  Figs.  4  and  5  (irregular  octagon  and  double  crescent). 

Sizes  A.  Another  typical  illustration  of  the  schemes  used  by  all  the  subjects 
in  the  sizes  of  the  simultaneous  set.  The  correct  order  was  5416372.  Her 
system  consisted,  she  says,  of  three ‘sky-lines:’ the  first  a  descending  one  formed 
by  the  terms  541,  the  second  an  ascending  one  formed  by  the  terms  167,  the 
third  an  ascending  and  descending  one  formed  by  the  three  smallest  terms. 
Despite  the  small  total  area  of  the  series  and  consequently  greater  difficulty 
in  discriminating  the  terms  the  system  served  its  purpose  pretty  well.  After 
13  days  and  many  series  learned  in  the  interval  the  subject  got  the  whole  series 
correct  except  a  single  exchange,  the  smallest  and  third  smallest.  She  remem¬ 
bered  and  used  the  system  in  reconstruction,  but  forgot  the  third  ‘sky-line.’ 

Col.  Forms  IIL  Influence  of  an  introspection  series  given  two  and  one-half 
months  before  causes  the  subject  to  put  Fig.  5  (inverted  hat)  in  ist  place,  where 
a  figure  of  the  same  shape  and  size,  but  red  instead  of  yellow  had  stood.  The 
other  errors  are  displacements  caused  by  this  change. 

Col.  Forms.  IV.  All  correct. 

Col.  Forms  II.  Poorly  recalled  and  no  special  reason  evident. 

Sizes  I.  Same  result  as  in  Col.  Forms  II. 

Forms  A.  Its  mediocre  retention  is  explicable  on  the  basis  of  its  extremely 
short  learning  time,  10  secs.  The  equal-armed  cross.  Fig.  3,  is  put  in  5th 
place,  where  the  larger  long  blue  cross  was  in  C.  F.  d.  S.  II,  20  days  before. 
The  other  errors  are  exchanges  of  adjacents. 

Forms  III.  In  learning,  a  similarity  between  Figs.  6  and  7  and  the  number 
10  was  noticed.  In  final  test  Fig.  4  took  the  place  of  Fig.  6  in  this  idea.  This 
brought  Figs.  3  and  5  together  forming  an  unnatural  looking  low  ‘sky-line’ 
at  this  point,  which  R  broke  by  putting  Fig.  2  between  Figs.  3  and  5.  The 
two  latter  were  also  transposed.  Note  their  similarity. 

Col.  Sizes  III.  In  learning,  the  only  error  was  an  exchange  of  6  and  7, 
which  are  not  only  similar  to  each  other  in  size  (and  in  color  to  this  subject), 
but  are  also  similar  to  the  two  largest  areas  of  Sizes  II  (learned  at  the  same 
time)  in  respect  to  the  positions  occupied.  The  exchange  was  a  copy  of  the 
positions  of  6  and  7  in  the  other  series.  Same  error  repeated  in  the  final  test, 
and  also  made  by  the  subject  next  to  be  discussed. 

Sizes  II.  Confused  with  the  series  just  mentioned.  In  final  test  6  and  7 
were  placed  as  they  should  have  been  in  that  series.  Further  errors  in  this 
series  were  moving  4  to  left  end  and  i  to  a  place  in  the  middle,  both  in  imita¬ 
tion  of  Col.  Sizes  III.  The  remaining  errors  cannot  be  traced. 


84 


HARVET  ANDREW  PETERSON. 


Cols.  III.  Her  learning  scheme  was:  ‘group  of  the  left  three  were  pronounced 
colors,  yellow  first,  purple  and  red  next,  the  last  two  a  displeasing  combina¬ 
tion.  Group  of  the  right  three  consists  of  a  pale  one  (green  tint)  followed  by 
two  neutral  colors.  Blue  associated  with  middle,  a  conspicuous  position.’ 
In  final  test  the  left  three  were  correctly  recalled,  but  green  gray  was  put  in 
the  middle,  with  which  place  a  gray  had  been  connected  in  the  week  interven¬ 
ing  between  the  learning  and  final  test  of  this  series  (viz:  in  Cols.  IV).  The 
cue  for  the  right  three  was  forgotten. 

Sizes  III.  Too  poorly  recalled  to  analyze.  The  left  three  have  the  regu¬ 
larly  increasing  size  arrangement  of  the  original,  but  do  not  begin  with  the 
exactly  correct  size. 

Col.  Sizes  IV.  An  almost  complete  copy  of  her  last  week’s  arrangement  of 
Col.  Sizes  III,  which  she  had  recalled  uncommonly  well.  The  order  there 
was  34(55172  instead  of  34751(52.  The  order  here  was  346527/.  The  only 
difference  is  an  exchange  of  the  two  smallest.  This  is  very  different  from 
what  the  series  should  be,  viz:  3162547. 

Sizes  IV.  Too  poorly  recalled  to  analyze.  Her  arrangement  is  similar  in 
a  general  way  to  the  original  in  the  fact  that  each  wing  consists  of  a  large  one 
flanked  by  smaller  ones,  but  the  wings  are  exchanged. 

Forms  IV.  In  final  test  exchange  of  Figs.  5  and  6,  due  to  the  identity  of 
Fig.  7  with  a  part  of  Fig.  5.  The  confusion  of  similars  most  frequently  shows 
itself  by  an  exchange,  partial  or  complete,  but  it  seems  not  unlikely  that  at 
other  times  it  results  in  bringing  together  the  terms  confused.  This  is  very 
plainly  the  case  here  and  in  Cols.  IV  with  the  next  subject,  N.  The  remaining 
error  in  Forms  IV  was  an  exchange  of  Figs,  i  and  3. 

Cols.  IV.  In  learning,  red  and  green  in  3d  and  5th  places,  with  gray  between 
them,  formed  a  group.  The  complementary  character  of  red  and  green,  noted 
by  the  subject,  is  both  a  help  and  a  risk.  They  were  exchanged  once  in  learn¬ 
ing,  and  in  final  test  green  is  again  put  in  place  of  red,  the  latter  being  dis¬ 
placed  to  2d  place.  The  other  error  consists  in  putting  blue  tint  in  6th  place, 
where  R  had  wrongly  put  a  similar  color  last  week.  (Green  blue  in  Cols.  HI.) 

Subject  N. 

Cols.  A.  Influenced  by  Cols.  II  learned  the  week  before,  three  colors  being 
placed  as  were  similar  colors  in  that  series.  Blue  is  moved  from  1st  to  3d 
place,  red  from  7th  to  5th  and  green  from  5th  to  6th.  The  other  errors  result 
from  these  displacements. 

Forms  I.  Exchange  of  adjacents.  Figs.  4  and  5. 

In  discussing  four  of  the  series  immediately  following  this  chronological 
table  will  be  of  service. 


INFLUENCE  OF  COMPLEXITT  AND  DISSIMILARITY  ON  MEMORY.  85 


7th  week.  Learned  Sizes  B  and  Col.  Sizes  I. 

8th  week.  Learned  Sizes  C  and  Col.  Sizes  11. 
gth  week.  Final  test  of  Sizes  B  and  Col.  Sizes  1. 

loth  week.  Final  test  of  Sizes  C  and  Col.  Sizes  11. 

Sizes  B.  The  correct  order  is  3416275.  In  final  test  the  subject  gave 
3451726, — an  exchange  of  sizes  6  and  7,  and  a  removal  of  5  to  3d  place.  The 
latter  error  gives  a  longer  ‘sky-line’  in  the  first  three  terms,  a  peculiarity  which 
may  have  been  due  to  Sizes  C  learned  the  preceding  week.  Both  the  peculiar 
shape  of  the  terms  in  this  latter  series  and  their  order  (26,  457,  13)  emphasized 
lines  ascending  to  the  right.  All  of  the  subjects  spoke  of  this  and  considered 
it  rendered  the  series  easier. 

Col.  Sizes  1.  Same  erroneous  idea  of  pronounced  upward  slope  in  the  final 
test  of  this  series.  Instead  of  the  correct  order,  2317645,  3457126  is  given. 
From  the  point  of  view  of  size  this  cannot  be  anything  else  than  two  upward 
slopes. 

C.  F.  d.  S.  III.  Exchange  of  Figs.  5  and  7.  No  similarity. 

Forms  11.  Two  exchanges  of  similar  forms.  Figs.  2  and  5,  and  3  and  6. 

C.  F.  d.  S.  IV.  Fig.  8,  a  small  inverted  hat,  moved  to  the  left  of  Figs.  4 
and  5.  No  reason  apparent. 

Col.  Sizes  11.  Final  test  was  the  same  as  in  Sizes  B,  with  a  slight  change. 
Here  it  is  2351746.  There  it  was  3451726. 

Sizes  C.  In  the  final  test  the  subject’s  arrangement  was  3451726,  the  correct 
order  being  2645713.  This  is  exactly  the  same  mixture  of  B  and  C  which  the 
subject  employed  in  the  final  test  of  B,  a  week  before. 

Col.  Forms  IV.  One  displacement.  Fig.  6  moved  to  the  left  of  Fig.  4. 

Cols.  11.  All  correct, — very  unusual.  His  scheme  was:  ‘The  heaviest  (red) 
with  the  two  lightest  (yellow  and  green  tint  i)  on  either  side,  were  next  to  the 
right  end  (4th  to  6th  places).  Of  the  remainder  a  light  one  (orange  red  tint  2) 
was  on  the  left  end  followed  by  two  heavy  ones.  The  one  in  7th  place  was 
correctly  placed  by  being  left  over  after  the  others  had  been  arranged.’ 

Cols.  I  and  B.  I  preceded  B  a  week  in  learning.  In  final  test  I  shows 
plainly  the  influence  of  subsequently  learning  B.  The  only  error  is  a  removal 
of  green  yellow  and  red  orange  shade  from  6th  and  7th  places  to  2d  and  3d, 
and  a  consequent  rightward  displacement  of  2-5.  This  is  approximately  the 
position  of  a  bright  red  and  yellow  in  B,  namely,  3d  and  4th  positions.  B, 
however,  is  also  affected  in  its  final  test  the  next  week.  The  interference  is 
mutual.  Aside  from  an  exchange  of  adjacents  (5th  and  6th)  the  only  error 
is  a  removal  of  green  from  7th  to  2d  place  where  a  bright  green  stood  in  1. 

Col.  Sizes  A.  The  errors  are  due  to  a  confusion  of  terms  within  the  series, 
similar  to  each  other  in  size  and  color.  All  of  the  subjects  experienced  this 
diflSculty.  The  similarities  in  color  constituted  a  defect  in  the  series,  and 


86 


HARVEY  ANDREW  PETERSON. 


were  one  of  the  reasons  why  it  was  rejected  from  the  regular  series.  In  the 
case  of  this  subject  the  errors  were  an  exchange  of  3  blue  and  4  blue  green, 
and  of  5  green  tint  and  6  A-green  yellow. 

C.  F.  d.  S.  I.  Two  exchanges  of  adjacents. 

C.  F.  d.  S.  II.  This  series  shows  interference  of  other  series.  Only  the  ist 
and  4th  are  correctly  placed.  Fig.  7  (spire)  is  moved  to  second  place  occupied 
by  a  figure  of  the  same  shape  but  different  color  and  larger  in  Col.  Forms  II 
seen  5  days  before  .  Fig.  5  (tall  cross)  is  put  in  3d  place  occupied  by  a  maltese 
cross  of  a  very  different  color  and  size  in  C.  F.  d.  S.  IV.  Fig.  2  (trademark)  is 
put  in  6th  place.  The  same  figure  but  very  much  larger  and  of  slightly  dif¬ 
ferent  color  had  been  in  7th  place  in  C.  F.  d.  S.  IV.  Fig.  3  (pin-wheel)  is 
put  in  7th  place  where  a  figure  of  the  same  shape  but  different  color  and  size 
had  been  in  Forms  II.  C.  F.  d.  S.  IV.  and  Forms  II.  were  last  seen  31  days 
before. 

Col.  Sizes  B.  Recall  too  poor  to  analyze. 

Forms  B.  Fig.  4  moved  to  ist  and  Fig.  7  to  4th  place.  No  explanation. 

Sizes  A.  Exchange  of  sizes  2  and  3,  and  4  and  5. 

Col.  Forms  I.  Exchange  of  adjacent  Eigs.  4  and  5. 

Col.  Eorms  II.  All  correct.  The  subject  said:  “Eigs.  3,  4,  and  5  were 
recalled  by  the  appearance  of  the  three  as  a  group.  Figs,  i  and  7  were  asso¬ 
ciated  with  their  positions,  and  Figs.  2  and  6  were  contrasted  with  each  other 
and  associated  with  their  positions. 

Forms  A.  Interference  of  other  series.  Fig.  7  (wide  vase)  put  in  first  place 
where  a  slender  vase  of  different  color  had  been  in  C.  F.  d.  S.  II  12  days  before. 
Exchange  of  Figs.  5  and  6.  Fig.  3  (equal-armed  cross)  put  in  7th  place  for 
no  apparent  reason. 

Sizes  I.  Exactly  the  same  arrangement  as  was  given  for  Sizes  C  43  days 
before! 

Sizes  II.  In  learning  the  only  error  was  arranging  the  series  once  in  the 
exact  arrangement  of  Col.  Sizes  III.  Despite  the  correction  which  it  had 
received,  the  same  mistake  was  made  in  final  test,  the  only  alteration  being 
an  inversion  of  the  last  two  terms. 

Col.  Sizes  III.  An  illustration  of  the  fact  that  the  interference  is  always 
mutual.  This  series  and  Sizes  II,  learned  at  the  same  time,  were  confused 
with  each  other.  The  other  series  fared  the  worst,  but  in  the  final  test  of  this 
series,  6  and  7  were  arranged  as  they  were  in  that  series.  There  was  also  an 
inversion  of  the  last  two  terms,  as  in  Sizes  II. 

Col.  Forms  III.  Fig.  5  (inverted  hat)  put  in  1st  place,  occupied  by  a  figure 
of  the  same  shape  and  size,  but  different  color,  three  months  before  in  an  intro¬ 
spection  series.  The  only  other  error,  aside  from  the  rightward  displacement 
of  figs.  1,  2  and  3,  was  an  exchange  of  the  similar  figures,  4  and  6  (tombstone 
and  knobbed  oblong). 


INFLUENCE  OF  COMPLEXITY  AND  DISSIMILARITY  ON  MEMORY.  87 


Forms  III.  One  error  in  final  test,  an  exchange  of  the  obviously  similar 
figures,  3  and  5  (pentagon  and  pentagon  with  curved  upper  sides). 

Colors  III.  The  errors  were  two  exchanges:  one  of  green  yellow  and  orange 
yellow,  similar  colors,  the  other  of  colors  not  similar.  The  association  of  a 
smaller  figure  of  the  same  color  as  one  of  them  with  the  place  where  one  of 
these  two  is  put,  may  have  been  the  cause.  The  interval  was  a  week. 

Sizes  III.  In  final  test  the  arrangement  is  quite  similar  to  the  correct  order 
in  a  general  way,  but  not  in  detail.  Instead  of  2451376  is  given  3561274. 
This  series  and  the  next  two  are  good  illustrations  of  interference  within  a 
series  due  to  poor  perceptual  discrimination,  the  kind  which  Ranschburg  found 
in  his  six-place  numbers.  The  very  fact  that  the  arrangement  is  similar  only 
in  its  general  contour  as  a  whole  shows  incomplete  perceptual  discrimination 
of  similar  things,  of  the  kind  that  he  found. 

Sizes  IV.  Confused  with  Sizes  III,  learned  at  the  same  time.  Once  in 
learning  it  was  given  as  3461275,  the  correct  order  of  Sizes  III  being  2451376. 
The  only  other  error  made  in  learning  was  a  removal  of  3  from  one  end  to  the  other. 
In  the  final  test  there  was  a  general  resemblance  to  the  correct  order.  3741265 
is  given  in  place  of  4761253.  It  is  true  that  the  correct  orders  of  III  and  IV 
somewhat  resemble  each  other,  but  in  the  former  the  two  largest  are  on  the  right, 
while  in  the  latter  they  are  on  the  left  end.  In  the  final  arrangement  of  IV, 
the  largest  is  back  in  place. 

Col.  Sizes  IV.  I  and  4  exchanged  in  final  test,  due  to  an  exchange  of  3  and 
4  in  learning.  Cf.  their  positions  in  the  correct  order,  3162547. 

Forms  IV.  Adjacent  Figs.  2  and  3  exchanged  in  final  test. 

Col.  Forms  IV.  Figs.  5  and  7  exchanged.  No  similarity. 

Cols.  IV.  Too  poorly  recalled  to  analyze.  Black,  ist  place,  and  gray,  4th 
place,  moved  to  3d  and  2d  places  respectively, — an  instance  of  similars  brought 
together. 

There  were  also  6  exchanges  of  numbers  belonging  to  sizes  nearest  each 
other  in  area,  which  occurred  during  the  learning  of  some  of  the  above  series, 
and  which  have  not  been  heretofore  mentioned. 


